What caused a teacher to have a complete breakdown?

Woohoo, do I have a story for this one?

A few years ago, I took a class in design theory.

It was the pet project of the head of the college, and taught the design principles

behind everything from common household objects to room layouts to entire organizations.

It was an absolutely brutal class, but uniquely informative. One day,

towards the end of the semester, we went over the use of humor in design. The professor

spent the entire class talking about how laughter and amusement can be used to engage

an audience and change how people see a situation. The whole time he was laughing, cracking

jokes, good ones too, and generally making

sure the class had a good time. At the end of the lesson, he told us not to underestimate the

power of laughter. After all, it was how he had gotten through the lecture that day. His father had

died a couple of days prior. He broke down crying after he told us. It's probably the most impactful

lecture I've ever attended.

The teacher in question was bullied and disrespected every day. One day, an idiot threw a geometry

compass and it stuck in the corkboard like a thrown knife right besides her while she was writing

on the board. Instant meltdown. She was in tears, she left the class, and I never saw her again. I can't blame

her. She probably thought her life was in danger at that point. Some schools and neighborhoods are very hard.

The teacher learned that one student had cheated on a history essay. After getting this kid suspended

for two days, repeat offender, she discovered that almost two-thirds of the class in that subject was cheating as well.

I don't know what happened after that, but she literally broke down when she found out that my class knew about it.

We were in a different subject, so we weren't part of that scandal.

...