Professors rated highly by their students tended to yield better results for students in their own classes, but the same students did worse in subsequent classes. The implication: highly rated professors actually taught students less, on average, than less popular profs.
Meanwhile, professors with higher academic rank, teaching experience and educational experience -- what you might call "input measures" for performance -- showed the reverse trend. Their students tended to do worse in that professor's course, but better in subsequent courses. Presumably, they were learning more.
I don't feel quite so bad anymore.