Supporting teachers’ participation in Lesson Study with Facilitators or Advisors: investigating the impact on their students’ mathematical reasoning

Lesson Study (LS), a collaborative and inquiry-based teacher professional development model, has received increased attention in recent decades. It involves teachers in small groups planning lessons, teaching them and then reflecting on them. While evidence exists on teachers’ satisfaction with participating in LS, evidence on the impact of LS on student learning outcomes is still scarce. This study examines (a) the impact of teachers’ participation in LS on students’ mathematical reasoning and (b) the impact of different types of support offered to the teachers. Secondary mathematics teachers (n = 132) in Belgium, Cyprus, and Greece were randomly split into three groups. Two experimental groups conducted LS, planning and reflecting on six lessons during the school year. They differed in terms of the type of support that they received in the LS meetings: the Facilitator guided teachers through the LS process and the Advisor also offered advice on teaching mathematical reasoning. Teachers in the control group did not conduct LS. Tests measuring mathematical reasoning were administered to students from two classes of each teacher at the beginning and end of the year. Multilevel analyses revealed that students in the Advisor group had better results. Implications for research, policy and practice are discussed.