Have you ever seen something happen in just a second or two that causes a person to have problems at school for weeks or even years afterward?
Example: I know about a girl who was randomly chosen from her science class to cough into a petri dish. Over the next week, the class got to watch the bacteria from her breath grow into a black, disgusting mass in the dish, and kids started to avoid her, because she was “contaminated”. They knew there was nothing wrong with her, but kids can be cruel.
Another example: A substitute teacher in my 5th-grade class affectionately called a rather tough boy “cream puff” one day. He was teased about being a “cream puff” for a long time after that.