There's no clip for it but it's one of my favorite jokes on the show that I rarely see mentioned and didn't catch it until my sophomore year of college. It's from Separate Vocations, the season 3 episode where the kids take a vocation test and Lisa gets homemaker while Bart gets police officer. Lisa becomes a burnout and Bart becomes hall monitor, leading to this awesome montage showing Bart and Skinner cleaning up the school and then the moment that made me spit cereal out in my dorm room:
Teacher: This is a great day for me. I thought I could never teach again!
Skinner: Oh, things have changed. There will be no mockery of your name, Mr. Glascock.