my cheeks can still flush when remembering some particularly bad ones -
When I was about 10, my foot went dead while sat on the floor for assembly. A particularly stern teacher had the job of ushering us out at the end - didn't want to get his attention so tried to walk on it and collapsed onto a group of the year above, who were in the row behind. Trying to break my fall, one of my hands landed directly on a boy's genitals and he started screaming. Then the teacher stood over me with his hands on his hips, shouting at me to get up as I lay flailing on the ground, trying to explain, with the whole year laughing. Worst bit was I had reflexively started patting the boys genitals immediately after it happened, in a kind of sorry/there there, make it better way.
There are so many more, mainly involving accidentally pissing myself at school. please tell me I'm not alone in never having gotten over these things!!