Generalizations about Using Value-Added Measures of Teacher Quality

The extensive investigation of the contribution of teachers to student achievement produces two generally accepted results. First, there is substantial variation in teacher quality as measured by the value added to achievement or future academic attainment or earnings. Second, variables often used to determine entry into the profession and salaries including post-graduate schooling, experience, and licensing examination scores appear to explain little of the variation in teacher quality so measured with the exception of early experience. Eric A. Hanushek, Hoover Institution, Stanford University, May 2010