„Some of the measures we now use to control schools have more error than others. One of the worst in this respect is the ‚value-added‘ estimates used to evaluate teachers in many states. These are highly imprecise, and ratings of many teachers fluctuate dramatically, sometimes wildly, from year to year.“
Univ.-Prof. Dr. Daniel Koretz, „The Testing Charade. Pretending to Make Schools Better” (2017), S. 15f