It is common knowledge that teacher quality is a key in-school factor affecting student achievement. While the quality of teaching clearly matters for how much students learn, this quality is challenging to measure. Evaluating teacher quality based on the level of their students' end-of-year test scores has been one method of assessing…

The evaluation of teachers based on the contribution they make to the learning of their students, "value-added", is an increasingly popular but controversial education reform policy. In this report, the authors highlight and try to clarify four areas of confusion about value-added. The first is between value-added information and the…