Lesson Study (LS), a collaborative and inquiry-based model of teacher professional development, has received increased attention in recent years. It involves teachers in small groups identifying an issue in their teaching practice and organising an inquiry to learn more about it. Specifically, teachers jointly plan, teach and reflect on lessons. A rich body of mostly descriptive and qualitative studies suggests that with LS experience teachers may develop pedagogical knowledge, and may be able to identify students’ misconceptions (e.g. Cheung & Wong, 2014; Vrikki, Warwick, Vermunt, Mercer & van Halem, 2017). However, more large-scale controlled studies are needed in order to systematically evaluate the effect of LS (Benedict et al., 2023). In addition, even less evidence exists of the impact of teachers’ participation in LS on their students’ achievements (e.g. Cheung & Wong, 2014; Kager, Mynnott & Vock, 2023). 

In addition, variations of the LS model include the presence of an external expert (i.e., LS facilitator, knowledgeable other, moderator). The literature identifies many ways that this external expert can support teachers, including enhancing in-depth discussions about students’ thinking, shaping the quality of the teachers’ inquiry, fostering teachers’ discussions by posing questions, encouraging teachers to share their experiences and managing the LS process (e.g. Akiba et al., 2019; Schipper et al., 2017; Bjuland & Helgevold, 2018; De Vrie, Verhoed & Goei, 2016). These responsibilities are not only vaguely described, but their effects have not been studied either. At the same time, research on teacher and school improvement argues for the important role of an advisory and research team that can work closely with teachers and support their attempt to design, implement and evaluate their action plans (e.g., Creemers & Kyriakides, 2012; Scheerens, 2013).

This paper addresses both limitations in the literature described above. First, it aims to examine how secondary mathematics teachers’ participation in LS affects their students’ achievement in reasoning. Second, it aims to examine how different types of support offered to LS teacher groups can further enhance students’ achievement. Specifically, it examines the impact of the support of a LS facilitator, who guides teachers through the LS process, fosters their discussions and promotes teacher learning which is expected to affect student learning outcomes. It compares this to the impact on student learning outcomes of the support of an LS advisor who in addition to guiding teachers through the LS process, offers subject advice and his/her own ideas to the teachers. Although having these kinds of support is not uncommon, little is known about the effect of different types of support that teachers may have in implementing LS. 

A group randomisation study took place in Cyprus during the school year 2022-2023. A total of 42 lower secondary mathematics teachers, who taught Grades 7 to 10 (students aged 11-14), in 13 secondary schools, were randomly allocated to three groups: two experimental and one control group. Teachers in two experimental groups formed small LS teams (2-3 teachers) and implement a specific variation of the LS model, namely Dudley’s (2019) “Research Lesson Study”. This is a three-cycle model, meaning that to complete one LS teachers had to plan three “research” lessons, one teacher teaching them while the others observed, and then to jointly reflect on the lessons. Each LS team completed two LSs during the school year, that is six research lessons. The difference between the two experimental groups was that teachers in one experimental group were supported by a “LS Facilitator”, who coordinated the discussions and helped teachers through the LS process, while teachers in the second experimental group were supported by a “LS Advisor”, who also provided advice on mathematics pedagogy. Teachers of the control group did not participate in any LS. Two classes per teacher were randomly selected to participate in the study, giving a total of 966 student participants. The students completed mathematical reasoning tests at the beginning and at the end of the school year. Specifically, a total of five tests were developed by a group of mathematics educators and expert teachers to assess students’ cognitive learning outcomes in relation to mathematical reasoning. These tests were used as pre-tests and post-tests across the four grades. Prior to the intervention, the construct validity of the five tests was examined. Data were analysed by using the Rasch model and support to the validity of the tests was provided. Student background data (i.e., students’ socioeconomic background and gender) were also collected via a student questionnaire.

Using one-way ANOVA, it was found that there was no statistically significant differences on student prior achievement among the three groups at the beginning of the intervention. Inferential analysis revealed no statistically significant differences at .05 level in terms of student background characteristics (i.e., SES and gender). To search for the impact of the intervention on student learning outcomes, multilevel analysis of student achievement in mathematical reasoning was conducted for the data collected at the end of the intervention. The empty model revealed that the teacher level rather than the class level should be considered for this analysis. In Model 1 prior achievement in mathematical reasoning was added as an explanatory variable. Prior achievement was found to have a statistically significant effect on final achievement. In Model 2, student background variables including grade were added as explanatory variable. Finally, two dummy variables (with the control group treated as a reference group) were added to model 2. Only the dummy variable concerned with supporting teachers with an advisor to implement LS was found to have a statistically significant effect at .05 level. Thus, the multilevel analysis revealed that students whose teachers participated in the Advisor group had better results in mathematical reasoning than students whose teachers participated in the Facilitator and the Control groups. Implications of findings for research, policy and practice are discussed. The paper argues about the role of advisor which seems to be crucial for promoting student learning outcomes. Policy makers and school leaders, therefore, should consider options for creating the conditions for in-school models of professional development. Further research is needed to test the generalisability of the findings.

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