more closely related to existing policy proposals. In analyses both of teacher mobility and of student performance, teacher … salaries are shown to have a modest impact. Teacher mobility is more affected by characteristics of the students (income, race …Important policy decisions rest on the relationship between teacher salaries and the quality of teachers, but the …

Much of education policy focuses on improving teacher quality, but most policies lack strong research support. We use … student achievement gains to estimate teacher value-added, our measure of teacher quality. The analysis reveals substantial … variation in the quality of instruction, most of which occurs within rather than between schools. Although teacher quality …

that teacher mobility is much more strongly related to characteristics of the students, particularly race and achievement …

disentangles the separate factors influencing achievement with special attention given to the role of teacher differences and other … effects on achievement differences, these effects appear to derive most importantly from variations in teacher quality. A … lower bound suggests that variations in teacher quality account for at least 7« percent of the total variation in student …