Will try to keep it brief but might end up being quite lengthy.
Background: DS (8) moved schools about 18 months ago after some quite violent bullying (kicked in the head, punched, hit with rocks etc). Boy in question was meant to have one on one care at school but still managed to attack my child at any given opportunity. School said it didn't meet threshold for expulsion, that they couldn't watch this child 24/7 and if said child ran off from one on one care then they couldn't physically restrain him from hitting my son. After meetings with LEA and school governors I decided to move my son when it became apparent they would do fuck all.
New school is somewhat better but as friendships had already formed my son is sometimes feeling excluded and there's some lower level stuff (name calling) that is quite frequent. There was one major incident at the beginning where another child pulled down my childs swimming trunks in the changing room and touched him. I went to social services, the school, the boys parents - again this child was meant to have one on one care but apparently this doesn't include the changing rooms. Nothing much was done.
Yesterday: Teacher comes over at home time and informs me that my DS was hit in the face at lunch time by a boy in year 6 (so 10 or 11yrs). She didn't give me much information other than that the boys parents were being called in. We leave but later on in the evening we bump into the boy and his mum on a shopping trip, DS loudly exclaims "That's the one mum, that's the one who hit me". Boys mum and I have a chat and she informs me of SEN and that her son is known (by school) to seek out younger and vulnerable children when he is stressed to attack them and lo and behold he is meant to have one on one support.
I'm fucking furious. The school are failing both of our children surely? Why is one on one support not working?
My son is awaiting an ASD assessment. When things like this happen he tends to blame himself for being 'stupid, ugly, fat' (he is none of those things) 
Unfortunately he then tends to hurt himself (bangs head against wall, swallows lego, previously asked me to hide all the knives in the house).