The rest of the day's waffling

I wanted to have a word with Little Prince's teacher about the Ed Psych's visit, but she wasn't in today so I couldn't! I'll have to catch her tomorrow instead. Although I am a bit miffed that she was told before Little Prince joined her class that we needed to be kept informed if there were going to be any staff changes, as this can sometimes send Little Prince overly waffy!
And on the subject of overly waffy!! I was talking to my friend (Little Prince's girlfriend's mum) at swimming and she was telling me what had happened at school today. Little Prince had been swinging one of the 'stilts' (see picture) round by its rope, let go of it and it had hit another child and badly cut her head. I know the child's mum so immediately rang up and apologised and asked how the child was, she has had to have butterfly stitches and has a slight headache, but is otherwise ok. I could have cried. How? Why? What was going on?? According to the child's mum (who lives directly opposite school so can see what goes on in the playground) all the children do that and no one has thought to stop them, and I'm not to blame Little Prince. She is writing a letter complaining about the lack of supervision (her older child was also hurt today by an even older child throwing stones at him!!) during breaktimes. I don't know what to do! My child was the "aggressor" here, but the school know he has issues and I warned them he would probably be worse this week (due to the upheaval of LMS going back to Uni and missing her) and he had a different teacher. He was probably a ticking timebomb and unfortunately this time someone has got hurt. I know what Little Prince is like, he is no angel, but he wouldn't deliberately hurt another child (well apart from his sisters!!) BUT he gets carried away and once he is revved up he finds it almost impossible to calm back down again. He NEEDS very close supervision, not the teachers/dinner ladies standing in the doorway drinking their cuppas and not taking any notice of the kids - which I've observed on more than one occassion!!