Over the last two decades, research on student achievement has pinpointed the central role of teachers. While other factors—families, peers, neighborhoods—are obviously elements in a student’s learning, it is the school and particularly the teachers and administrators that are given the public responsibility for the education of our youth. There is a general consensus that improving the effectiveness of teachers is the key to lifting student achievement, although questions remain about how best to do this.
A key element in focusing attention on the importance of teacher effectiveness was research that took an outcomes-based perspective. By looking at differences in the growth of student achievement across different teachers instead of concentrating on just the background and characteristics of teachers, it was possible to identify the true impact of teachers on students. This work, now generally called value-added analysis, demonstrated that some teachers consistently get greater learning gains year after year than other teachers. In fact, the average learning gains associated with a teacher provide a convenient metric for teacher effectiveness.
We now have a substantial number of studies that indicate clearly how much difference teacher effectiveness makes to student outcomes. In one study of mine, teachers near the top of the quality distribution got an entire year’s worth of additional learning out of their students compared to those near the bottom. That is, a good teacher will get a gain of 1.5 grade level equivalent while a bad teacher will get 0.5 year during a single academic year. Importantly, this analysis considered kids just from minority and poor inner-city families, indicating that family background is not fate and that good teachers can overcome deficits that might come from poorer learning conditions in the home.
Importantly, there is now direct evidence that the Washington, D.C., personnel policies are paying off. Thomas Dee and James Wyckoff found that dismissal threats increased the voluntary attrition of low-performing teachers by more than 50 percent. Additionally, low-performing teachers who stayed improved their performance significantly, as did high-performing teachers who were in the range to get bonuses.
Similarly, the Los Angeles Unified School District has moved to remove around one hundred poorly performing teachers. While this remains small compared to the total number of teachers in Los Angeles, it is orders of magnitude larger than what was seen just a couple of years ago.
Many states and localities are developing what must be thought of as experimental programs for ensuring teacher quality. The key to the future is validating and replicating the ones that prove successful and eliminating the ones that do not. Doing this requires a strong research and evaluation activity to match the policy experimentation.