Nazarbayev Intellectual School (NIS) is an educational institution focused on providing quality education to students in Kazakhstan. The school aims to develop students' knowledge and skills in various areas, including language and content learning, through a variety of pedagogical approaches. One of the approaches that has proven to be beneficial to student learning is Content-Language Integrated Learning (CLIL). CLIL is a teaching and learning approach that combines language and content in an integrated way (Marsh, 2010). In recent decades, this teaching approach has gained popularity in many countries around the world (Hussain, 2022). The aim of CLIL is for students to learn both the target language and content knowledge more effectively in the same lesson. CLIL is also beneficial for teachers because it offers them the opportunity to become more proficient in the target language and to expand their pedagogical knowledge and skills. Although NIS is committed to quality education, there are still challenges in effectively implementing CLIL in classrooms. The challenge is to find an effective way to engage students in the learning process and ensure that they understand and make sense of the language they are learning. Furthermore, implementing CLIL can be challenging and requires a high level of teacher commitment to ensure success. Therefore, there is a need for effective teacher professional development to support teachers in implementing CLIL in their respective classrooms (Nhan, 2013; Garzón-Díaz, 2021).

This study proposes the use of the Lesson Study (LS) model to provide teachers with the necessary support and development for successful implementation of CLIL. The LS model encourages teachers to collaboratively plan, observe and reflect on their own teaching practise, which helps them to better understand CLIL principles and provides them with the necessary resources to successfully implement CLIL in their classrooms (Lewis & Lee, 2017). As part of the process, the teacher-researchers in this study observed each other's classes and discussed their observations together to increase their knowledge and skills related to CLIL and to identify areas for improvement (Takahashi, 2016). In this way, the LS model helps teachers to develop more confidence and competence in their CLIL teaching and to gain a better understanding of how to teach using different CLIL strategies. Furthermore, LS not only promotes collaboration between teachers, but also encourages them to share best practises, develop new teaching strategies and find innovative ways to incorporate more CLIL activities into their lessons (Willems & Van den Bossche, 2019).

The primary objective of this study is to investigate the effectiveness of the LS approach as professional development to strengthen CLIL instruction among teachers in NIS, as well as its effect on student academic achievement. The study focuses specifically on the professional development of educators in NIS Uralsk, Kazakhstan. NIS Schools and their network incorporate both the LS model and CLIL into their curriculum. LS and CLIL provide teachers with the opportunity to develop innovative lesson plans and instructional materials that challenge and engage students' learning and help them become more independent students. Moreover, these methods are essential for establishing a framework for teacher education programs across the NIS network.

In particular, the following research questions are addressed:

1. How does participation in the lesson study approach impact teachers' knowledge and skills in integrating content and language in their instruction?
2. How does the lesson study approach impact student academic performance in CLIL contexts?
3. How does the lesson study approach impact the quality of teaching and learning in CLIL classrooms?
4. What are the perceived benefits and challenges of the lesson study approach for teachers and students in CLIL contexts?

Research design: This research employs a mixed-methods approach, including qualitative and quantitative data collection and analysis. This design can provide a deeper understanding of the influence of the LS approach on teacher professional development and student academic performance. Participants: The participants in this study are eleventh- and twelfth grade CLIL teachers and their students from NIS Uralsk. A treatment group of teachers who participated in the LS approach as professional development for CLIL teaching will be compared to a control group of teachers who did not participate in the LS approach. Research instruments and data collection: Multiple research tools can be used to investigate the effects of the LS approach on teacher professional development and student academic performance in CLIL environment. These research instruments consist of: 1. Pre- and post-surveys: These can be used to evaluate teachers' attitudes and beliefs regarding CLIL and the LS approach prior to and following participation in a professional development program. 2. Interviews: Interviews with teachers and students can provide detailed information about their experiences with the LS approach and CLIL instruction. 3. Classroom observations (Mehisto, 2012): Observing CLIL classrooms before and after the implementation of the lesson study approach can provide insight into changes in teaching and learning practices. 4. Student assessments: The use of standardized tests or other measures of student achievement can provide information regarding changes in student academic performance as a result of the LS method. 5. Focus groups: Focus groups with teachers and students can provide a more in-depth understanding of their experiences with the lesson study approach and CLIL instruction. It is important to use a variety of research instruments to triangulate the data and get a more comprehensive understanding of the impact of the lesson study approach on teacher professional development and student academic performance in CLIL contexts. Data analysis: The collected data will be analyzed using both qualitative and quantitative methods. Qualitative data, such as interviews and observations, will be analyzed through thematic analysis to identify common themes and patterns. Quantitative data, such as student surveys and assessments, will be analyzed using statistical techniques to identify trends and relationships. Ethical considerations: All participants will provide informed consent prior to their participation in the study. Data will be collected and analyzed in accordance with ethical principles. All data will be kept confidential.

The findings of the study will help inform educators about the impact of CLIL on teacher professional development and student academic achievement and provide evidence-based strategies to strengthen CLIL instruction at NIS. In addition, the study includes the following findings based on the research questions: 1. Improved knowledge and skills of teachers in integrating content and language in their instruction. This outcome could be measured through surveys, interviews and classroom observations. 2. Increased student academic performance in CLIL contexts. This could be measured through standardised test scores or other measures of achievement, such as grades or assessments. 3. Enhanced quality of teaching and learning in CLIL classrooms. This could be measured through classroom observations or other measures of the quality of teaching and learning, such as student engagement or participation. 4. Greater understanding of the perceived benefits and challenges of the lesson study approach for teachers and students in CLIL contexts. This could be measured through surveys, interviews or focus groups. 5. Comparison of the effectiveness of the lesson study approach to other professional development methods in terms of its impact on teacher knowledge and skills and student academic performance in CLIL contexts. Overall, the significance of this study lies in its ability to enhance the quality of CLIL teaching at NIS and consequently improve student learning outcomes. This research has the potential to support the development of professional training programmes for CLIL teachers at Nazarbayev Intellectual School and other schools, and to contribute to a broader understanding of the effectiveness of the LS approach as a method for professional development in CLIL teaching. Finally, it is important to consider the implications of the study for practise and to share the findings with relevant stakeholders, teachers, students and policy makers.

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