Study: Use caution in rating teachers by student scores

A new federal study raises questions about whether it’s fair to use student test scores to measure teacher effectiveness.

In response to a request from the Nevada Department of Education, researchers examined whether the contribution of teachers to student growth could be teased out of test scores. The Regional Educational Laboratory analyzed three years of math and reading score data for about 370 elementary and middle school teachers from Nevada's second largest school district.

The researchers concluded, “This study finds half or more of the variance in teacher scores from the model is due to random or otherwise unstable sources rather than to reliable information that could predict future performance. Even when derived by averaging several years of teacher scores, effectiveness estimates are unlikely to provide a level of reliability desired in scores used for high-stakes decisions, such as tenure or dismissal.”