In childhood, in early years of school, I perceived teachers as evil and good. In the last years of school we used to label them as "normal" and "crazy" (or "idiots", if one preferred).

My grades were exceptionally high with "good" teachers and low with "evil" throughout all the school. Only recently I liberted myself to start seeing that as a good sign.

I guess, "good" or "normal" teachers in our perception were those who procrastinated from teaching these lessons.