Oh, have I got a terrible one. Let me see if I can make this, um, family-friendly.
When I was about 12, I had this very elderly teacher who was very strict about students going to the bathroom in the middle of class. She just did not give bathroom passes for anything, she said you were supposed to go in the break between classes. Well, you know how it is when you're just starting to, uh, be a woman...and sometimes the Red Tide shows up unexpectedly yet enthusiastically?
So I raised my hand and asked to go to the bathroom. Of course, she said no. Then, about 20 minutes later, she announced that it was my row's turn to collect the quizzes and bring them to her desk, so I got to walk around the whole classroom, squelching all the way. As I handed her the quizzes, a trail of blood all over the classroom behind me, and a giant puddle worthy of a Friday The 13th movie underneath my desk, I whispered, "Can I please go to the nurse? It's an emergency." She didn't even look up, but yelled at the top of her lungs, "Are you going to throw up?" I said no, it's just an emergency, I need the nurse. "If you're not going to throw up, it's not an emergency, go sit down and quit wasting my time!" She didn't even look at me, meanwhile the whole class was deadly silent except for little giggles. She went right back to teaching. Of course, after class I got to walk all the way across the building dripping blood and leaving bloody sneaker-prints in front of the whole entire school, to the nurse's office.
The nurse had to drive me home to get showered and changed, because my mother wasn't answering her phone at work, either.