Evidence that teachers' short-term instructional effects persist over time and predict substantial long-run impacts on students' lives provides much of the impetus for a wide range of educational reforms focused on identifying and responding to differences in teachers' value-added to student learning. However, relatively little research has…

Arguably the most important educational resource is teachers. Teachers and teaching quality are a central feature of the No Child Left Behind Act of 2001 (NCLB) which requires a "highly qualified teacher" in every core academic classroom. Many states and large districts also have policies in place to attract qualified teachers to…