This will a headache sorting out all the facts. This was in class, so one needs to get a sense of what the boy's intent was - immature joking, teasing, or part of a history of sexual harassment that we don't know about? Was he trying to expose her, or was he trying to get her attention and (in some grossly immature way) flirt? Did she need to defend herself with a weapon or just go to the teacher and report him?
It seems to me that facts need to be sifted, in cases like that, before random people on social media start deciding what really happened and then delivering judgments.