Using Technology to Support Teachers’ Lesson Adaptations during Lesson Study

Lesson study is a professional development activity that increases teachers’ attention to student thinking. However, coordinating teachers’ live observations of a lesson can be challenging. Using the framework of distributed cognition, we investigate whether technology supports teachers’ examination of student thinking and aids the processes of developing and archiving new knowledge about students’ mathematical understandings in lesson study. We use data from a professional development intervention where four geometry teachers discussed videos and animations within a lesson study cycle. We ask, (1) what modifications to the lesson did the teachers offer, and (2) what were the justifications and sources (i.e., videos, animations, or teacher lesson observations) of those modifications? Using a modified Toulmin model for arguments, we analyzed the teachers’ arguments about lesson revisions...