There is only one part of teaching that is really tedious, and that is grading papers. If you are grading wonderful papers, the only thing that is tedious is the sheer volume of them. If you are grading papers that are not so wonderful, it gets painful to keep hitting the same keyboard macro to insert [singular/plural mismatch] or [italics for book, magazine, journal, or movie titles]. (Yes, it is not all just hitting keyboard macros, but so much of marking up papers is remarkably repetitive, because the same mistakes happen again and again.)
The tedium of grading papers, however is a small price to pay in exchange for teaching. On the plus side, grading student papers means that you learn things that you did not know (once you verify that the student actually found something that you did not know and is correct). For example, if the Athenian assembly did not have enough citizens present to hold a vote, slaves would be sent into the streets with ropes dipped in red paint, to slap any citizens who were not present to make a quorum--a chance to shame them for their lack of civic-mindedness.