That the school year ended too swiftly and I couldn't give more snap quizzes. Seeing the look of terror when several students aren't prepared can make any teacher happy.
Yeah, I'd have to say the school year ending too early is what I hated most about school for more than 2 decades.
That and the frog fights.
Looking back at my actual attending school days:
By the time I reached high school, I didn't mind going, it was almost fun.
Except for math...
Senior year I had a math class at 7:30 a.m. in what had to be the coldest snowiest winter ever. Winter arrived early, around Halloween and wouldn't let up. I lived 3/4 of a mile from the school and had to walk there, it was pretty bad that first half. Then the final semester arrived, graduation was in sight. I had comedy classes: Electronics, Retail Management and Consumer Education, along with English. Three afternoons each week, I went with a pretty red haired girl to the local college where we took English and Psych courses.
So, I guess I didn't like math, other than that it was pretty much okay.