Teachers’ Continuous Professional Development through Lesson Study: Voices of Vietnamese EFL Teachers at University

This study investigated how teachers perceived the benefits and difficulties of implementing a Lesson Study (LS) in the context of English language teaching at a university in Vietnam. The data were collected from six teachers through semi-structured interviews. To analyze the data, two addressing themes (teachers’ perceived benefits and teachers’ perceived difficulties) were focused on while implementing LS. The results generally showed that the teachers believed that LS brought them three benefits: encouraging teachers’ exchange activities and helping them deepen knowledge of lesson content, understanding students’ learning activities and working processes, and promoting teachers’ motivation in pursuing their continuous professional development (CPD). Regarding teachers’ perceived difficulties in LS implementation, they reported lacking confidence in actively implementing LS activities. Additionally, they had difficulties in time management and encountered problems reaching a consensus for joint work due to the influence of muti-faceted aspects. Accordingly, the study provides pedagogical implications for related stakeholders (teachers, students, and policymakers) regarding LS implementation issues contributing to the success of LS implementation in Vietnam and other similar contexts.

eachers' continuous professional development (CPD) can be defined as a lifelong learning process that starts from the very beginning of teachers' teaching careers and continues until they stop or retire (Villegas-Reimers, 2003).CPD has become an influential norm in educational reforms, and it helps teachers to facilitate learning activities through which they can learn to adapt to new changing roles and teaching approaches (Mon et al., 2016).
Numerous empirical research has looked into the relationship between teachers' CPD and their teaching practices, which found that CPD has played a significant role in guiding teachers' profession (Alamri et al., 2018).Teachers' CPD is crucial to affecting teachers' beliefs and needs, which can change their practices to fit with a particular context (Tran & Pasura, 2021).Hwang (2021) states that teachers' CPD not only helps them learn modern tools and instructional approaches but also knows how to apply them in their practical-based teaching classrooms.Similarly, Mizell (2010) argued that CPD activities that assist teachers in deciding instructional strategies would best support students' learning.
It is not easy to successfully implement CPD programs for teachers.Guskey (2002) and Forrest (2018) stated that most forms of CPD for teachers are seen to be top-down and too isolated from classroom-based practices.Research shows that most activities for teachers' CPD are perceived as less relevant or even unconnected to classroom-based teaching practices (Elmore, 2002;Margolis et al., 2017).This trend is particularly true in the Vietnamese context, where most CPD activities normally take the form of one-shot training attempts and focus much on the what, not the how of CPD (Tran, 2016).Thus, the effects of such CPD activities are often undervalued.Needless to say, seeking a possible solution to the CPD for Vietnamese teachers should be a must.
Lesson Study (LS) appears as an innovative approach focusing on cooperation between teachers in classroom-based teaching practices contributing to strengthening their CPD (Murray, 2013).Moreover, LS emphasizes the classroom as the best place for the teachers' practices resulting in the development of their CPD (Stigler & Hiebert, 2009).However, it is foreseen that implementing LS in Vietnam seems to be a big challenge due to the impacts of the hierarchical system of policy-making on educational innovations and also the influence of the Confucian Heritage Culture in which collectivism, that is the extent to which people tend to form strong, cohesive groups, has still existed (Nguyen & Jaspaert, 2021).In an attempt to investigate whether implementing LS as an instructional approach for teachers' CPD in the Vietnamese context of English language teaching at the tertiary level is possible, this qualitative study was conducted to explore how Vietnamese teachers at a higher education institution perceived the possibility of LS implementation in terms of its benefits and challenges after they had gone through a period of LS implementation.Accordingly, pedagogical implications for enhancing the opportunity for LS implementation in Vietnam as well as other similar contexts, will be suggested.

Lesson Study
Since its beginnings in the 1960s in Japan, LS has placed a strong focus on the core value of the interaction between teachers and teachers and between teachers and students in classroom-based teaching practices.To clarify, LS is a structured process where teachers collaboratively plan, observe, analyze, and refine actual classroom lessons.It involves cycles of preparing, teaching, observing, and discussing lessons to enhance educational practices.It is believed that teaching, under LS perspectives, is a highly complex process that offers teachers ample opportunities to share pedagogical insights and think deeply about the work they do in the classroom.In this respect, LS requires deep thoughts, inquiries, and collaborations with a collective focus on classroom-based practices rather than teachers themselves (Murata & Lee, 2020;Stepanek et al., 2007).Murray (2013) believed that the concept behind LS is simple, stating that enhancing the quality of teaching and learning in schools requires teachers together to study teaching and learning processes and then have sound ways to improve their practices.In this respect, LS is a potential model mainly structured for promoting teachers' CPD through specific steps and favorable conditions during the implementation process.These steps typically include planning a lesson, observing how it unfolds in a live classroom setting, and conducting postlesson discussions.This cycle is integral to LS and forms the foundation of its "complex and interactive" nature.Fernandez and Yoshida (2004) and Bocala (2015) added that through LS, the teachers observe others' teaching, then try out similar lessons themselves.This process becomes central to the effectiveness of teachers' teaching profession.
LS is a long-established teacher-led collaborative approach that aims to develop teachers' professions as well as learners' learning outcomes (Fernandez & Yoshida, 2004;Wood & Cajkler, 2018).Though LS is centered on collaborative work among the teachers, it also creates a positive learning environment for learners while involved in lessons (Lewis & Perry, 2014).Chenaul (2017) supported the idea that collaboration in LS allows teachers to share their previously learned experiences or stories of ineffective or unsuccessful teaching with their colleagues.Moreover, collaboration in LS helps support teachers' revisions in the lesson, clarify misunderstandings or misconceptions while teaching, and effectively highlight areas that need improvement for better instruction (Howell & Saye, 2016).Wood and Cajkler (2018) emphasized that although the cycle of LS procedurally looks simple, it engages the teachers in a highly complex interactive process in practice.LS is considered a cycle of instructional improvement for teachers' CPD consisting of serial steps.This cycle begins with identifying a focus for the lesson, followed by collaboratively designing the lesson, observing the lesson in action, and finally, conducting a detailed postlesson discussion.Despite the fact that different researchers have developed their cycle for implementation depending on particular characteristics of individual institutions and working cultures, the working ideas behind the cycle open up for thorough preparation, revision, and implementation (Murray, 2013).

Related Studies
There have been quite a few studies on LS in countries such as the USA, Hong Kong, and Japan.Cheung (2011) conducted an experimental study in Hong Kong to measure the impact of LS on the teaching of teachers and students here in Chinese writing.The analysis was meticulously performed with pre-mid-posttests and lesson observations to collect data.The results showed that the teachers in the experimental group worked more effectively than those in the control group through the scores achieved by learners in the two groups.Specifically, learners in the experimental group became more creative when writing Chinese than their counterparts in the control one.Marble (2007) conducted a qualitative study in the USA involving 24 pre-service teachers teaching integrated science and mathematics.Through lesson observations, debriefing protocol, and summative portfolios, the data shows that many aspects of this group of preservice teachers increased rapidly, especially their teaching capacity, self-confidence, classroom management skills, and learner assessment ability.They also significantly improved their students' engagement in the classroom.Matoba et al. (2007) carried out their research in the Japanese context.This study was conducted as a case study using quantitative and qualitative data to determine the impact of LS on teachers' teaching of Japanese, social studies, science, mathematics, and English.Specifically, data were collected from students' academic results, the number of students dropping out, evaluation forms of teachers and students about the quality of education at the school, and teachers' reflections after using LS in their CPD.Regarding the results, most teachers thought LS was a highly effective professional development tool.They created a healthy work environment and professional and practical knowledge by collaborating, sharing, and evaluating each other's lessons.In addition, the students developed their knowledge quickly due to the increased teaching ability of teachers.They found the learning environment more effective, so the number of students absent from school decreased.
Many more studies conducted in South Africa, Tanzania, Sweden, Australia, the UK, and Singapore, also show the great potential of LS (Ming Cheung & Yee Wong, 2014).Ono and Ferreira (2010) conducted a case study in South Africa, highlighting the role of lesson study in teacher CPD.The study emphasized the significance of lesson study in promoting ongoing professional growth among teachers.Similarly, Kihwele (2023) explored the factors influencing the implementation of lesson study in pre-service teacher education in Tanzania, shedding light on the importance of lesson study in supporting teachers' CPD.Moreover, highlighted the importance of linking teacher PD needs with appropriate solutions, emphasizing the role of lesson-based PD programs in enhancing teachers' understanding of implementing 21st-century skills in the classroom (Eriņa & Namsone, 2021).LS has also been recognized as a model for developing teachers' competence, as demonstrated by Setiawati et al., (2021), who conducted research on pedagogical competence in pre-service biology teachers through lesson study.
Although the implementation of LS has been reported to be advantageous worldwide, research on the possibility of LS implementation in Vietnam is still underrepresented, especially in English teacher-related stories.Therefore, it is necessary to conduct a study investigating teachers' insight perceptions of the implementation of LS in EFL classrooms regarding their CPD.The study addresses the following questions: 1. What are teachers' perceived benefits of LS when implementing LS as an instructional approach for their CPD? 2. What are teachers' perceived difficulties when implementing LS as an instructional approach for their CPD?

Participants
This study occurred in the context of EFL teaching classrooms at a university in the Mekong Delta, Vietnam.Before conducting the study, the research team contacted the university and asked permission to conduct the research there.With the approval, the research team contacted English teachers in charge of teaching English language courses.Regarding the criteria for selecting participants, they had to be full-time teachers working at the same university and being in charge of teaching the same English language course at the time of the study.In addition, these teachers had to prove that they had no explicit knowledge of LS or any experience trying out LS in their practical teaching.To address this, the research team provided a comprehensive training program on LS, including its principles, practices, and implementation strategies.This training aimed to equip the participants with the necessary knowledge and skills to effectively incorporate LS into their teaching and observation practices.Initially, three groups with 23 teachers met the above conditions to become the official participants in this study.The first group has eight members, the second group has seven, and the last group has eight.For the first and second groups, each with more than half of the members, after hearing the research group disseminated the research content, refused to participate due to many reasons, most commonly due to time constraints.As a result, the number of remaining members was so small that these groups were not selected to participate in this study.As for the final group, only two members refused to join for the same reason as above, and the remaining six members agreed to join.Therefore, the six participants who decided to participate implicitly became the official participants of this study.Consequently, the participants were six EFL teachers (5 females and one male), with a mean age of 41.5.Regarding qualifications, they all had Master's degrees in Principles and Methods of English Language Education.Following the training, these teachers (n=6) implemented LS in their classrooms, which was observed and evaluated by the research team to ensure systematic application and to gather data on the impact of LS on their teaching practices.These teachers (n=6) had an average of 14.3 years of teaching experience and did not have any knowledge about LS.

Design
The present study employed a qualitative and case study research design to gain a fuller understanding of Vietnamese EFL teachers' perceptions of the implementation of LS.Qualitative research is believed to provide a rich and deep understanding of social phenomena.At the same time, the case study design allows the researchers to explore a case over time through detailed, in-depth data collection involving multiple sources of information rich in context (Creswell, 2012).Due to time and scope constraints, this study only focused on one case, a group of 6 tertiary teachers who tried out the implementation of LS in their English classes.

The Lesson Study Setting
The current study adopts a model of LS proposed by Murray (2013) comprising six phases.The researchers decided to adopt this model since it is said to be well-fitted and suitable for the teaching context where the study took place.

Phase 1: Forming and Focusing the Group
In this phase, six teachers teaching the same English course were invited to participate in the study.The teachers were all informed about the goals and related issues of LS implementation.Working as a team, under LS perspectives, requires that the teachers must always show their highest trust and commitment in a highly cooperative and supportive working environment.In fact, they had to discuss and share responsibilities for improving both their CPD and student learning.

Phase 2: Collaboratively Planning the Lesson
In this phase, the teachers had to recall their past knowledge and experiences and consider other conditional factors, such as materials, facilities, etc., to ensure they could discuss and best design the lesson for the LS implementation.Specifically, the teachers were first encouraged to work collaboratively on the content or concept to be taught.They also reached out to a so-called effective teaching method employed for their teaching practices.Next, the teachers had to describe the lesson in a detailed manner.Finally, the teachers had to come up with a joint agreement on how students' learning outcomes could be evaluated and outline a particular means of data collection for group members to follow when they observe the teaching of the lesson.

Phase 3: Teaching and Observing the Lesson
In this phase, one of the teachers in the group taught the lesson to the classroom while others observed and gathered data on the students' learning and their working processes.In addition, the lecture was also recorded to facilitate discussion and analysis after the lecture was over.
Data collected during this phase permits teachers in the group to reflect on the extent to which student learning did or did not progress and how each component of the lesson supported or impeded student learning.

Phase 4: Discussing the Lesson
After observing the lesson, all of the teachers sat together (right after school on the day of the lesson demonstration) to reflect on the lesson by discussing the data from the video and observation forms gathered during their lesson observations.As agreed before, the teacher who taught the lesson talked first to express his/her opinions on what went well and what did not, followed by the group members who took turns to share data and what it revealed to them about student thinking and learning.Whenever pointing out strengths and weaknesses, the group would use the video to replay the part they were talking about so that the whole group could better grasp the problem.

Phase 5: Revising and Reteaching the Lesson
In this phase, the group revised the lesson based on contributing ideas of the teachers leading to an updated version of the lesson.Then, a different teacher taught the revised lesson while others again observed and gathered additional data for further improvement of the lesson.

Phase 6: Discussing the revised lesson and summarizing the learning
In this phase, the group members met again to reflect on what they had observed from the teaching of the revised lesson.The teacher secretary of the group noted down members' shared points about their instruction, student learning, and thinking to ensure that a good record of the process was effectively made.Next, the group wrote up a summary of the entire LS implementation cycle, focusing on what has been learned about their teaching and student learning.
This process was repeated over the course of 14 weeks.All the above steps were strictly followed and not interrupted.The video recording of the class was also consented to by the students, so the research team was confident that none of the ethical values in the study were seriously violated.

Research Instrument
This study employed a semi-structured interview activity for data collection since it allows in-depth exploration into how the teachers perceive the implementation of LS for their CPD (Creswell, 2012).In addition, the semi-structured interview guide created the best conditions and freedom for the participants to express whatever ideas of their perspectives.Also, unstructured parts of the interviews allowed the researchers to collect any unanticipated data deemed vital and relevant to conceptualize the findings of the study.

Data Collection Procedures
This study was carried out over 16 consecutive weeks, including the first week for the LS orientation and the last week for the closing.Prior to the start of the study, one of the researchers emailed the teachers in the department to provide an information sheet about the study project and asked for their voluntary participation.
For data collection, the teachers had to implement LS within 14 weeks under the close supervision and facilitation of one of the researchers since that one was well-trained and familiar with the principles and techniques of LS.During this period, when other teachers were observing classes as part of the LS process, they utilized a structured evaluation method.This method included a detailed observation checklist and a reflective journal.The checklist was designed to focus on key aspects of teaching and learning within the LS framework, such as the effectiveness of lesson delivery, student engagement, and the application of new teaching strategies.Additionally, the teachers were encouraged to use reflective journals to document their observations, insights, and suggestions for improvements in a more narrative and subjective form.Furthermore, the researchers were present in some classroom sessions to observe the implementation of LS.This direct observation by the researchers aimed to provide an additional layer of data collection and to cross-verify the information gathered from teacher observations.At the end of the semester, face-to-face semi-structured interviews were conducted, allowing the participants to describe their experience of LS implementation in their own words.To allow for the teacher participants' best convenience and comfort, the interviews were conducted in Vietnamese, the mother tongue of both the interviewer and interviewees (Creswell, 2012;Tran & Phan, 2021).The participants were informed that they could end the interview or withdraw from participation at any time without penalty.During the interview, the researchers probed responses only for elaboration or clarification.
Each of the interviews lasted approximately 90 minutes, and they were all audio-recorded.All participants were interviewed once, with a potential for a second round if confusing views needed to be clarified or explained.Pseudo names (Teacher 1, Teacher 2, Teacher 3, Teacher 4, Teacher 5, and Teacher 6) were also created for the teachers in the narratives to keep confidential.The researchers transcribed the interview recordings verbatim, then coded data into themes.All the questions addressed teachers' perceptions of benefits as well as their perceived difficulties when implementing LS as an approach for their CPD.It is important to note that the presence of the researchers in the classroom could potentially affect student performance and behavior, which was considered in the analysis.The researchers observed a few discrepancies between their observations and those reported by the teacher observers, mainly in the areas of student engagement and the effectiveness of certain teaching strategies.These discrepancies were further explored during the interviews to understand the teachers' perspectives and interpretations of the classroom dynamics.

Data Analysis
The data of the study were analyzed by using a thematic method.To ensure the credibility of the analysis, several steps were taken.First, the interview transcripts were first coded through an integrative process, involving multiple researchers to cross-check and validate the coding.
This was followed by a meticulous process of categorizing the coded data into two emerging themes (teachers' perceived benefits and difficulties in implementing LS) guided by the two research questions.Additionally, to enhance the reliability of our thematic analysis, we conducted periodic peer reviews and discussions among the research team.Murray's (2013) framework with six steps of LS implementation was used as a guideline for categorizing the LS-related issues emerging during the process of LS implementation.This framework, being well-established in the field, further added a layer of rigor to our analysis methodology.

Findings Teachers' Perceived Benefits of Lesson Study for their Continuous Professional Development
The results indicated that all of the teachers (n=6) believed that LS had positive impacts on encouraging teachers' exchange activities, allowing them the best opportunities to share ideas and receive constructive feedback from their fellow teachers.Teacher 3, for instance, said: "I realized that this model (LS) has created a very cooperative working environment where other teachers and I could actively and freely discuss the teaching lesson, exchange experiences, or share things happening in the classroom."In the same vein, LS was said to offer the teachers favorable conditions to sit together to "discuss the lecture, to share ideas on effective teaching and also to figure out possible problems (Teacher 4)".
It is also revealed that the teachers received significant contributions and constructive feedback from their fellow teachers while participating in the LS model.As reported by the teachers, they could not precisely evaluate the success of their classroom teaching, for instance, how to know whether the students did well in their learning (Teachers 2, 3, and 5) or how to address what the students were not satisfied with (Teachers 3, 5, and 6).Through LS, however, the teachers could share data they collected (as an observer) or listen to feedback (as a teacher being observed) which might help them understand more about student learning.One of the teachers, for instance, mentioned: "Through accumulated ideas and feedback given by other teachers, I can uncover many hidden issues regarding my student learning" (Teacher 3).The teachers also admitted that through LS, they are equally respected in expressing their opinions regardless of their status, whether they are more or less experienced or old or young teachers.Teacher 2 said: "We are absolutely free to express our ideas or give feedback to others on the basis of mutual respect rather than criticism."Similarly, Teacher 6 reported: "I work in the spirit of mutual respect, sharing and giving suggestions for mutual improvement, not to criticize who is good or who is bad." The results showed that most of the teachers (n= 5 out of 6) agreed that LS helps them much in deepening knowledge of the teaching lesson through different means of sharing discussions contributing to adjusting their teaching methods to fit with students' learning.Teacher 2, for instance, expressed that through collaborating with the teachers in the group before and after conducting classroom-based teaching, she could "gain a deeper understanding of the teaching content" because she had to "explain questioned issues with clarification and negotiate with other teachers in order to come up with a common agreement."As a result, this suggested possible adjustments or even a complete change in her teaching methods.Similarly, teacher 4 admitted that he could "realize my strengths and weaknesses regarding my understanding of the lesson content through working with fellow teachers," which accordingly enabled him to make necessary changes in teaching.The teachers also reported that through observing others' teaching, they could gain better knowledge and experience of teaching such as "I could consciously know what is good, what is bad and thus I can do my teaching at best" (Teacher 6), "this enabled me to explicitly see the connection between what the teacher taught and what the students learned.I could also learn how to analyze, draw conclusions, and modify my future teaching" (Teacher 3).
The results additionally showed that most of the teachers (n=5 out of 6) believed that through LS, they could better and effectively understand students' learning activities, thereby adjusting their teaching accordingly.To illustrate, Teacher 1 shared that when she observed the student learning, she could "learn more about the process of students' acquiring knowledge."Other teachers also showed that they could identify several students' addressing needs, for example, "I know what support students really need in relation to their learning processes" (Teacher 2) or "how students are grasping the lesson content, how they are interacting with each other" (Teacher 1) while observing them learning.The teachers also reported that they obtained valuable information about student learning from their fellow teachers' sharing of collected data from classroom observations.One teacher reported: "Thanks to the input from my colleagues, I obtained useful information about the student learning such as whether they were bored or excited or whether they could understand the lesson content and so on" (Teacher 6).
The results indicated that half of the teachers (n=3) held a strong belief that LS helps promote their motivation on the path to CPD.Under LS perspectives, it is evident that the teachers had to take active roles in participating in activities that are suitable for their CPD, as reported by a teacher: "It is never enough for us to learn.You know, when joining LS, we had to actively participate in activities organized by the group where we needed to show our responsibility and therefore learned a lot" (Teacher 3).In this respect, teacher 3 felt "confident and more motivated in my teaching career."Similarly, Teacher 4 added: "LS is an important catalyst for teachers like me to get more motivation to develop my professional skills […].Now I am very motivated and willing to implement LS as an approach for my CPD".

Teachers' Perceived Difficulties in Lesson Study Implementation
The results indicated that all of the teachers (n=6) showed a lack of confidence in joining discussions during the first stage of LS implementation, mainly due to their poor knowledge of LS and sedentary working habits during the early implementation stage.Teacher 4, for instance, reported that he found it "really hard to figure out what to do, and how to do it […].I am not confident and ready to do it" because LS was relatively new to him.Regarding teachers' working culture, while implementing LS, it is admitted that they were still "passive and not really willing to share views" (Teacher 6).Similarly, Teacher 5 shared: "Most of the teachers did not like sharing their ideas with others.They tended to be quiet and tentatively listen rather than being an active speaker in discussion".
All teachers (n=6) participating in the study shared a standard view that it is hard for them to manage their time so as to participate in LS activities thoroughly.All teachers reported that they had to frequently and regularly meet the group to discuss the working plans, prepare lesson plans, and so on while carrying out a hefty teaching load assigned by their university.Teacher 4, for instance, said that: "You know, we each have a different and busy teaching schedule assigned by the university, so it is complicated to make an appointment," or "I have to teach four subjects this semester.I have to prepare the lesson and go to classes very often which takes me much time" (Teacher 6).In addition, some teachers (n=3) reported having to do extra tasks, i.e., teacher supervisors, research work, or community service besides their assigned teaching work.Therefore, it is tough for them to "arrange a suitable time for the whole group to meet together" (Teacher 1) because the teachers had to do many tasks at the same time, as reported by Teacher 3, stating that: "[…] being a teacher supervisor, I had to meet students, help them with paperwork and other stuff".
The results showed that all the teachers (n=6) reported difficulties making a joint conclusion or decision when working together.One teacher reported that "it is not easy to reach consensus due to the fact that different teachers shared different points of view about the same thing" (Teacher 2).Another teacher recalled: "Because we shared different points of view when working together, disagreement is inevitable.You know, it is tough to come up with consensus because everyone wants their opinions to be used" (Teacher 6).In addition, teachers' fear of making others lose faces or be judged as disrespectful prevents the teachers from giving direct and constructive feedback resulting in impeding the effectiveness of the LS implementation, which occurred during the early stage of the implementation.For instance, one teacher expressed: "I think that if I give feedback too directly and seriously, I am afraid of making them lose face or upset.So, I just said something around the corner" (Teacher 5), or in the case of Teacher 1, who reported: "When I first joined the project, I did not dare to express my opinions directly and constructively.You know, I need to show my respect to others".

Discussions and Implications
Regarding the first research question, the results showed that most of the teachers agreed on the idea that LS was influential in encouraging teachers' exchange activities which might create the best opportunities for them to share ideas and receive constructive feedback from their fellow teachers contributing to developing their CPD (Mon et al., 2016;Matoba et al., 2007).A possible explanation for this finding could be that LS requires teachers' collaborative participation in sharing activities with their fellow teachers so as to reach a consensus for the improvement of instructional practices (Wood & Cajkler, 2018;Marble, 2007).This reflects previous research stating that one of the actual values of LS is evaluated through the process of teachers' active participation while collaboratively working with their peers (Chenaul, 2017).Another possible explanation could be that LS encourages the teachers to be honest, productive, and constructive in discussion (Murray, 2013).Fellow teachers are encouraged to show their ideas and feedback in a manner of mutual respect rather than criticism.Therefore, the teachers are said to be more confident and actively engaged in discussion (Bozkurt & Ozdemir, 2016;Marble, 2007).From these perspectives, this study suggests that educational leaders need to place top priority on supporting teachers with policies in favor of promoting collaboration.Building a broader collaborative culture that recognizes the value of group work allows the teachers to interact with each other's knowledge and practical skills more comfortably and efficiently.
All teachers participating in the study also agreed that LS helps them deepen their knowledge of the lesson, contributing to their teaching skills.Additionally, this may enable the teachers to adjust their instructional methods to fit their student outcomes.This finding can be explained by the fact that LS creates favorable conditions for the teachers to plan teaching strategies and logically conduct the lesson through its different steps (e.g., collaboratively planning, discussing the lesson, etc.) (Mon et al., 2016;Stepanek et al., 2007).By doing this, it ensures that all the teachers in the group could be better equipped with sufficient knowledge of content, student agents, instruction, and so on, serving back to their CPD as well as satisfying the need for student learning (Matoba et al., 2007).Another possible explanation could be that LS allows the teachers to experience the lesson through teaching themselves and observing others' teaching.Needless to say, teaching and teaching observations followed by reflection on teaching significantly deepen the teachers' acquired knowledge to varying degrees (Mon et al., 2016;Özdemir, 2019;Cheung, 2011).It is, therefore, suggested that the teachers should facilitate more occasions for members' narrative sharing and self-critique.To promote this, it is necessary for the leaders, one of the key catalysts of the implementation, to have policies in which the teachers should be member-led.In other words, the teachers need to be considered the owners of the whole implementation process rather than passive doers and feel as if they are being forced to do the implementation.
The teachers also agreed that LS allows them to understand their students' learning activities and processes more.It could be explained that when the teachers visited the classroom engagements, they could gather evidence about a student, their motivation, or any reactions to the teaching.This might help them better understand student understanding knowledge and skill in specific areas (Murray, 2013).LS can be an effective tool to collect data about students' learning and address needs in different ways, such as classroom observations, teachers' notes, and the like (Matoba et al., 2007;Mon et al., 2016).This finding agrees with Bozkurt and Ozdemir's (2016) study, which stated that LS helps increase teachers' knowledge of students' learning.In fact, teachers cannot cover all student activities by focusing on their teaching.However, when they observe someone else's class, they can see more clearly what students do and do not do.This helps them somewhat adjust their teaching style.Therefore, policies to encourage teachers to participate more in classroom observations need to be proposed and implemented on a broader scale.In the spirit of mutual development, both the observing teacher and the observed teacher need to have a spirit of cooperation and demand.
It is also reported that the teachers were highly motivated when implementing LS as an approach for their CPD.This can be explained by the teachers' realization of the benefits and valid values of LS, particularly when they become more confident and active in collaborating with other teachers and professionals in their teaching (Chenaul, 2017;Marble, 2007).Jhang (2020) stated that the teachers participating in LS feel that they could gain a lot of valuable things such as self-confidence, professional status, attention from colleagues, and so on, which have an effect on their motivation in particular and their profession as a whole.It is, therefore, implied by educational leaders and policymakers that they have to encourage teachers to employ LS more frequently and continuously.Creating favorable conditions and motivating them, by all means, might help the teachers maintain their motivation to continue LS.Otherwise, it can be possible that implementing LS is unlikely to be successful since this approach requires much time and personal effort from the teachers (Özdemir, 2019).
Regarding the second research question, the results indicated that the teachers were not confident in working with others during the early stage of the implementation.One possible reason for this could be that because this group of teachers had not ever been trained or introduced to LS, they were, needless to say, unfamiliar with the knowledge and practices of LS.Another possible reason could be evident in teachers' shyness and passive working styles.They tended to be passive listeners rather than active speakers (Nguyen & Jaspaert, 2021).Therefore, it is suggested for the success of LS implementation that, before the implementation, necessary policies and supporting actions regarding issues of LS implementation must be taken into consideration to ensure that the teachers are well prepared and have a clear mindset about what they are doing.Furthermore, to promote teachers' active roles and confidence in joining group discussions, more training activities should be provided to develop teachers' understanding of LS (theoretically and practically).
It is also reported that the teachers in the study had difficulties in time management.It is undeniable that time management is likely to be a big concern since the teachers had to take a heavy workload assigned by the university, and they had to implement LS at the same time (Mon et al., 2016).Regardless of the teachers' creativity and flexibility in scheduling activities for the implementation, they had troubles with regard to time management.It is therefore suggested that educational leaders and policymakers need to take immediate actions, for example, reducing the workload to give place for the LS implementation or giving the teachers more favorable conditions (e.g., available resources, financial support, equipment, and facilities) enabling them to do the implementation more successfully (Mon et al., 2016).It is also noted that the teachers need to be faithful volunteers who show the best effort, devotion, and commitment to the success of the LS implementation (Eraslan, 2008;Fernandez & Yoshida, 2004).
The results also revealed that all teachers had difficulties reaching a consensus for joint conclusions and decisions while implementing LS.This finding was unsurprising because different people share different views on the same thing, as reported by many of the teachers in the study.In addition, it is possible that the teachers were afraid of breaking good rapport with fellow teachers.Vietnamese people have been heavily influenced by the ideology of the Confucian Heritage Culture, stating that collectivism and hierarchical relationships must be a focus (Nguyen & Jaspaert, 2021).Therefore, it could be the case that the younger or less experienced teachers in the study tended to agree with the older or more experienced ones, although they were not satisfied.From these perspectives, it is suggested that setting standard rules as a norm for the teachers before they officially work together should be a good idea since this might help them build a clear vision of the everyday working culture and acknowledge the value of collaborative work (Özdemir, 2019).In addition, it is worth mentioning that the presence of experts in the field of LS plays a crucial role in guiding teachers to consensus (Stepanek et al., 2007).By extending knowledge and other related issues in LS implementation, the expert can provide fellow teachers with professional support and means to conduct the implementation, especially by sharing ideas and developing a common agreement for joint discussions and decisions.Therefore, it is suggested that choosing a suitable person who needs to be fully prepared with knowledge of LS and shows excellent levels of enthusiasm for promoting LS implementation is vital to the team coach (Demir et al., 2013).
Last but not least, the current study's findings, where teachers adapted their teaching methods based on collaborative discussions and self-reflection, align with previous research indicating that LS fosters a culture of continuous learning and experimentation among educators.For instance, a study by Rappleye and Komatsu (2017) also found that LS encouraged teachers to innovate and adapt their teaching strategies, leading to enhanced pedagogical practices.Additionally, the use of various materials in LS, as indicated in this study, supports the findings of Leavy and Hourigan (2016), who reported that LS participants often introduce new resources or modify existing ones for greater effectiveness.This parallels the current study's indication that teachers likely altered educational materials based on feedback and discussions during LS sessions.Besides, the evolution of teachers' behaviors towards more reflective and feedback-oriented practices, as seen in this study, is consistent with the findings of Akiba and Wilkinson (2016), who noted that LS promotes a reflective and collaborative teaching culture.The current study extends this understanding by specifically highlighting the increased openness to feedback and willingness to experiment.The significant contribution of LS to teachers' CPD in this study is in line with Holden (2023), who found that LS provides a platform for professional learning through collaborative practices.The current study enriches this perspective by detailing how LS facilitates sharing, feedback reception, and observational learning, leading to professional growth.

Conclusions
It was apparent that the teachers participating in the study addressed certain benefits of LS significantly contributing to their CPD, such as encouraging teachers' exchange activities and helping them deepen their knowledge of lesson content, understanding students' learning activities and working processes, and being more motivated in pursuing their CPD.However, the teachers who approached LS in this study could not avoid specific difficulties throughout the project.It is reported that the teachers had to deal with issues of time management and the teachers' lack of confidence in taking active roles in group work.They also encountered difficulty reaching a consensus for joint work due to the influence of muti-faceted aspects.
This study significantly contributes to the existing literature on LS and CPD in the context of Vietnamese education.By highlighting the practical application of LS in a Vietnamese university setting and its impact on teachers' professional growth, the study provides valuable insights into the adaptability and effectiveness of LS in a non-Western context.This is particularly relevant given the limited research on LS in Southeast Asian educational settings.The findings underscore the potential of LS as a viable method for teacher development in diverse educational contexts, thereby expanding the understanding of LS beyond its traditional Japanese roots.
Beyond mere recommendations, this study offers tangible implications for educational practice.It underscores the need for educational leaders and policymakers to actively support and facilitate LS implementation, which is crucial for its success.This includes providing resources, training, and time for teachers to engage in LS.Additionally, the study emphasizes the importance of teachers' mindset and adaptability in embracing LS.This insight can guide teacher training programs to focus not only on the technical aspects of LS but also on cultivating a collaborative and active working culture among teachers.
However, it is important to acknowledge certain limitations of this study.Firstly, the study was conducted in a specific university setting in the Mekong Delta, Vietnam, which may limit the generalizability of the findings to other contexts, both within and outside of Vietnam.Secondly, the study involved a relatively small sample size of teachers, which may not fully represent the diverse experiences and perspectives of all teachers in similar settings.Finally, the study's focus on teachers who had no prior experience with LS might have influenced the outcomes and experiences reported.Future research could expand on these findings by including a larger and more diverse sample of teachers, including those with prior experience in LS, to provide a more comprehensive understanding of LS's impact on CPD in various educational contexts.