Hi Dark empathy
Your story is very simmelar to my boys. Started off with bullying by one boy but ended in SA by more than one. happened at brake times in the toilets and play ground because no teachers on duty.
He was beaten up so badly one day that my daughter phoned me from school because she could not find him, when I got there I found him hiding away, a split lip and a swolen eye. This was about 2 weeks before I moved him.
At this stage I did not know about the SA, we got his report for end of term this repot with his behavior of late rang worning bells for me. He got 80% for most of his subjects they also got scored for relating to teachers and pears where my son failed acording to his rapport. This for a boy that's an extruvert and can talk to anybody. I told him I could see something is wrong and I would love to help and that I could not help if he did not tell me what was going on. That is when he told my husband and I what was happening.
My husband went back to the principal to go and talk to him. Until to day nobody at the school denied what happened to my son acording to them we are just overreacting boys will excperiment and do things like this to each other. My son and this boy was nevver friends, this boy always bullied my son and as far as they were concerned
sorry have to go son just walked in mama