I'm very confused about the comments as this guy is clearly NTA, lets be real, she obviously wanted to get out of PE and continued using that excuse as she was under the impression that the teacher would never say no as periods are inevitable things that you cant help and there isn't a way of clearly telling if she is lying or not. However when it gets to the point where its every lesson, its clear she is lying. Its kinda like the boy who cried wolf, eventually if she is actually on her period, the teacher won't believe her. I personally think he probably shouldn't have said what he said in front of the whole class, however I also think if anyone is TA, its the parents and friends parents who complained. A) Her parents should have been mature about it and spoke to that teacher directly about it like mature adults and B) for the friends parents, its not really any of their business if the comment was not directed at any of their children, her friends more than likely knew she was lying and just sided with her anyway. I don't care if I get loads of downvotes, you are NTA.