In order to provide policymakers with a better understanding of the nature and stability of teacher effectiveness, this study estimates teacher effects over a relatively long period of time, in order to determine how stable various measures of teacher quality are from year to year and over different periods of a teacher’s career. We do this using a unique dataset from North Carolina that allows us to match students—who are tested in math and reading on an annual basis—to their teachers and to track both over time.

This aspect of the data allows us to answer some fundamental questions about the nature and stability of teacher effectiveness that are key to informing a wide array of teacher policies, ranging from teacher placement to professional development to compensation. Specifically, we investigate the following questions:

1) How stable are estimates of teacher performance across years and points in a teacher’s career?

2) Does teacher performance differ by subject area?

3) Are estimates of teacher performance more stable in some education settings?