In the wake of high-profile evaluations of teachers using their students’ test scores, such as one conducted by the Los Angeles Times, a study released last month suggests some such methods, called “value added” measures, are too imprecise to rate teachers’ effectiveness.
Among the problems, conclude researchers from the Annenberg Institute for School Reform, at Brown University, is that schools do not use a single, vertically aligned test for each subject, which is needed to track growth, and tests do not cover all state standards proportionately. The authors argue that value-added measures are most accurate for teachers with many years of student data, and less useful for novice teachers, who are more likely to need feedback.
