Value-added: not ready for prime time

Professor Bruce Baker has an excellent breakdown on so-called "value-added" evaluation of teachers and why (Race to the Top and measures around the country aside) it isn't ready for use...and maybe never will be:

I often explain that if we lived in a society that walked everywhere, and a new automotive invention came along, but had the tendency to burst into a ball of flames on every third start, I think I’d walk.