The National Council on Teacher Quality

Value-added measures are often criticized for providing a narrow view of a teacher’s performance. Conversely, broader measures like observations are seen as too subjective. A new study shows–happily–that both types of evaluations are consistent and complementary: they predict future students’ achievement. Teachers who score well on one also score well on the other. Best of all, combining them produces a stronger and more accurate measure of a teacher’s effectiveness than using either alone.
Jonah E. Rockoff and Cecilia Speroni of Columbia University looked at the ability of three measures to predict teacher effectiveness: a rigorous job application process, observations and ratings by trained mentors, and value-added calculations based on students’ math and English scores.