"One method [of measuring teacher quality] is to evaluate teachers based on their impacts on students’ test scores, commonly termed the 'value-added' (VA) approach. A teacher's value-added is defined as the average test-score gain for his or her students, adjusted for differences across classrooms in student characteristics such as prior scores. School districts from Washington D.C. to Los Angeles have begun to use VA to evaluate teachers. Proponents argue that using VA can improve student achievement... while critics argue that test score gains are poor proxies for a teacher’s true quality...

We find that students assigned to higher VA teachers are more successful in many dimensions. They are more likely to attend college, earn higher salaries, live in better neighborhoods, and save more for retirement. They are also less likely to have children as teenagers..."