Why didn't they ask Gelman?

Reformers like Cerf, Klein, Weisberg, and even Secretary Duncan often use the term "value-added scores" to refer to how they would quantify the teacher evaluation process. It is a phrase that sends chills down the spine of most teachers'-union officials. If, say, a student started the school year rated in the fortieth percentile in reading and the fiftieth percentile in math, and ended the year in the sixtieth percentile in both, then the teacher has "added value" that can be reduced to a number