Audrey Beardsley reveals the answer to the intriguing question: Why is D.C. hiding VAM data? The answer was earlier leaked to blogger and retired math teacher G.F. Brandenburg. Beardsley cites him in this post.

The VAM data show that VAM is junk science. Keep it a secret. D.C. school officials are trying to.

“In Brandenburg’s words: “Value-Added scores for any given teacher jumped around like crazy from year to year. For all practical purposes, there is no reliability or consistency to VAM whatsoever. Not even for elementary teachers who teach both English and math to the same group of children and are ‘awarded’ a VAM score in both subjects. Nor for teachers who taught, say, both 7th and 8th grade students in, say, math, and were ‘awarded’ VAM scores for both grade levels: it’s as if someone was to throw darts at a large chart, blindfolded, and wherever the dart lands, that’s your score.”