OP, just another point of view here:
My son befriended a boy who was in care, new to the same school as him, a year older.
The friendship gradually cooled to the point where it became antogonistic and hostile. The lad took against DS (9) and would take every opportunity to thump him. After a while of fuming and talking it out with DS (who is mouthy I must say), I had to advise him to run for the hills whenever he was approached by this boy.
I couldn't trust DS not to stoke it up verbally, but I now view it as a real safety issue. This boy is obviously prepared to go far further than most 10 year olds and I can't have him at risk.
The school contacted me by phone one day, to tell me the boy had gotten someone to hold DS's arms behind his back whilst he was strangling my boy and punching him in the stomach. This was the worst ina long chain of incidents, certainly not an isolated one.
I got the impression that it was stopped really quickly and that the teachers were more concerned about the potential danger than DS was about the attack.
The school has instructed them now to keep away from one another and even allocated them separate classes next year, they were that worried. I was assured that they were watching them like hawks, to the extent DS got a yellow card for approaching and antagonising the other lad, which I thought was fair enough.
I am not angry any more, I don't "need" the other lad to be punished: they just cannot socialise ever because I and the school, are really concerned about DS's safety.
I maybe haven't articulated it very well, but I guess I am trying to show you that it mightn't be malicious on the whole, they just might have the tigress instinct, like you do. They just want to protect their young.
I hope it works out for you and your DDs.