So here is my take on a shitty teacher.

I once had a microcontroller teacher, who tried to teach a class of non programmers how to code, from a broken compendium. While he was teaching he would correct errors that he found. Most of the classes would be pure theory on C and no exercises.
Needles to say after the first two semesters none of the students could program, and over half of the class had left the school.