Reflective lesson study for developing teachers’ PCK for modelling and epistemologies of models

Modelling is a central scientific practice, yet many science teachers still present models as fixed depictions rather than tentative, evidence-constrained tools. This reflects both teachers’ pedagogical content knowledge (PCK) for modelling and their epistemologies of models (EoM). Professional development addressing both dimensions remains limited. This study investigates Lesson Study (LS) as a mechanism for reshaping EoM and strengthening modelling-specific PCK. Five secondary science teachers engaged in two LS cycles over five months. Data from lesson observations, reflective dialogues, and interviews were inductively analysed to identify mechanisms of teacher learning. Four features of LS proved powerful: (1) self-reteaching, where teachers re-implemented revised lessons to transform reflection into enacted change; (2) critical reflection and dialogue, which tied instructional adjustments to student evidence; (3) knowledgeable others as catalysts, who injected theoretical clarity and challenged assumptions; and (4) master teachers as anchors, who grounded discussions in pedagogical expertise. These mechanisms shifted instruction from transmissive presentations of models towards constructivist engagement in generating, evaluating, and revising models. The study contributes a process model of LS as “plan – do – see–(self)reteach,” positioning self-reteaching as a novel catalyst of growth. Findings highlight how epistemological aims can be embedded in LS to support sustainable teacher learning.