Geometry education is an important aspect of STEM education and career development, but it is often overlooked in K-12 education in the United States. Although there is some research on teaching geometry to students with learning difficulties at the elementary level, there is a lack of research on teaching advanced geometry skills at high school…

The study reported in this article addresses the question of how professional development can increase teacher noticing of student thinking over time. The data come from five teachers' participation in a two-year professional development intervention that combined lesson study, video clubs, and animation discussions. The analysis focuses on…