Teachers Matter

People often emphasize the importance of good teachers, and many local, state, and federal policies are designed to promote teacher quality. Research using student scores on standardized tests confirms the common perception that some teachers are more effective at improving student test scores than others, although standardized tests provide an incomplete window into teachers’ overall effectiveness.

• Teachers matter more to student achievement than any other aspect of schooling.

  Many factors contribute to a student’s academic performance, including individual characteristics and family and neighborhood experiences. But research suggests that, among school-related factors, teachers matter most. When it comes to student performance on reading and math tests, teachers are estimated to have two to three times the effect of any other school factor, including services, facilities, and even leadership.

• Although researchers do not usually observe nonschool factors, statistical methods can provide valuable estimates of teachers’ effectiveness, but these estimates are imprecise.

  Researchers cannot directly control for most nonschool factors that affect student test scores. Statistical methods such as value-added modeling have been shown to produce valuable information about teachers’ effectiveness at increasing student test scores, but these estimates can be imprecise, especially for teachers who are early in their careers or who are new to a district. In addition, standardized tests do not measure all the outcomes that teachers are responsible for promoting, so measures based on these scores provide incomplete information about teachers’ effectiveness. Even with these caveats, research shows that high value-added teachers also influence longer-term outcomes, such as graduation, college attendance, and earnings.

• Effective teachers are best identified by their performance, not by their background or experience.

  Despite common perceptions, effective teachers cannot reliably be identified based on where they went to school, whether they are licensed, or how long they have taught. A better way to assess teachers’ effectiveness is to look at their on-the-job performance, including what they do in the classroom and how much progress their students make on achievement tests. This has led to policies that require evaluating teachers’ on-the-job performance, based in part on evidence about their students’ learning.