How do professional development programs on comparing solution methods and classroom discourse affect students' achievement in mathematics? The mediating role of students’ subject matter justifications

Comparing solution methods fosters strategy flexibility in equation solving. Productive classroom discourse such as Accountable Talk (AT) orchestrated by teachers can improve students' justifications during discussions and achievement. Do subject matter mediate the effect of teachers' professional development (PD) programs focused on comparing AT students’ mathematics achievement? We investigated whether two PD (comparing or comparing+AT) compared to a control group increased number students justifications, this affected achievement (strategy flexibility, procedural knowledge, conceptual knowledge). The study (739 9th 10th grade 39 classes) had an experimental pre-post design. Both significantly group. results our multilevel path models showed significant small mediation effects comparing+AT knowledge. No were found