. . . [W]e find that our measure of teacher effectiveness is negatively correlated with the students’ evaluations of professors: in other words, teachers who are associated with better subsequent performance receive worse evaluations from their students. We rationalize these results with a simple model where teachers can either engage in real teaching or in teaching-to-the-test, the former requiring greater student effort than the latter.That is from the paper "Evaluating Students' Evaluations of Professors" by Braga, Paccagnella, and Pellizzari.