I had a friend in high school who posted a blog about his Economics teacher. She wasn't a nounce, but she was still incredibly weird. Very obviously drunk during class. Would periodically just wander off and leave the room for long stretches of time. Incredibly temperamental towards the students. No discernible lesson plan. So we had this day-by-day log of all the crazy shit that went down in class.
The running joke was that she had dirt on the principle, because that's the only way she could have kept her job.
Anyway, despite this open and notorious record of her terrible teaching, she still hung on for another three or four years before finally getting let go.