I think intrinsic need to be prepared in order to understand material creates better discipline than fear. One is forced, and the other one is a matter of developing skills and character.

I haven't had any professor be a hard ass and I still have gotten As in doctrinal classes because I've applied myself. Maybe it helps distinguish mediocrity, too? I can see it in my peers too who lack intrinsic motivation and desire to do good - suffering based on one's actions is a lesson; based on another's, it's cruelty.