The long-term effects of teachers

Value-added models in education are used to attempt to measure the contributions to student achievement of individual teachers. Test scores for a particular teacher’s students are compared to those of the same students in the previous year, as well as to those of students with other teachers in the same grade, in an effort to isolate the contribution of the given teacher. Advocates of these methods argue that these measures provide objective information that can be used to improve instruction, while critics counter that their validity as an indicator of teacher quality is still in question. School districts from Washington D.C. to Los Angeles have started to use value-added measures, and some teachers’ ratings have been made publicly available, including recently in the Los Angeles Times and the New York Times.