Evaluating the quality of teaching: can there be valid differentiation in the middle of the performance distribution?

An important challenge in evaluating the quality of teaching is to arrive at valid distinctions between teachers, particularly in the middle of the performance distribution. This study addressed this issue for the Chilean national teacher evaluation system. Mathematics teachers (N = 51) from the 2 middle adjacent performance categories, and their students, were examined by videotaping classroom practice and coding the videos with the Classroom Assessment Scoring System for Secondary School, measuring students' perceptions of their teachers' practices and assessing student learning on standardized grade-level and unit-specific tests. Findings show that on almost all criterion variables, competent teachers outperformed basic teachers, but differences were usually small. Teachers evaluated as competent obtained consistently better results regarding their teaching practices, as assessed by trained observers, as well as based on reports by their own students. However, there was only weak indication of differences between the 2 groups in terms of student learning. [ABSTRACT FROM AUTHOR]