There is mounting evidence of substantial "teacher quality gaps" (TQGs) between advantaged and disadvantaged students but practically no empirical evidence about their history. We use longitudinal data on public school students, teachers, and schools from two states--North Carolina and Washington--to provide a descriptive history of the…

Education agencies are evaluating teachers using student achievement data. However, very little is known about the comparability of test-based or "value-added" metrics across districts and the extent to which they capture variability in classroom practices. Drawing on data from four urban districts, we found that teachers were…