The Geometry Assessments for Secondary Teachers (GAST) Classroom Observation Tool classifies the teaching moves and instructional tasks of teachers according to cognitive demand. It is designed for use specifically within math lessons focused on similarity, congruence, surface area, and volume. It can be used by teacher educators and researchers to identify the quality of math instruction within this domain.
Mohr-Schroeder, M., Ronau, R. N., Peters, S., Lee, C. W., & Bush, W. S. (2017). Predicting Student Achievement Using Measures of Teachers’ Knowledge for Teaching Geometry. Journal for Research in Mathematics Education, 48(5), 520–566.