Leading mathematician debunks ‘value-added’ 

By Valerie Strauss

This was written by John Ewing, president of Math for America, a nonprofit organization dedicated to improving mathematics education in U.S. public high schools by recruiting, training and retaining great teachers. This article originally appeared in the May Notices of the American Mathematics Society. It gives a comprehensive look at the history, current use and problems with the value-added model of assessing teachers. It is long but well worth your time.