My son hit a girl with a bike chain

We have a to go to court now over this. My son has been being bullied by the same 5 kids the entire school year. They had gotten violent with him a few times by slamming him to a locker. He was pushed down the stairs (that person got suspended) and stole his phone and broke it. It's been a lot of stuff. At school yesterday he was trying to fix his bike and took the chain off and the group came over and the girk kicked him in the face which made his nose bleed and he snapped and took his chain and hit her in the face. They were at first just gonna suspend him even when we watched the camera and she kicked him in the face first.

See I'm not the type of parent who tells my son not to hit girls. You don't hit ANYBODY unless to defend yourself and they didn't consider this seof defense since she only did it once. A girl should not either way put hands on someone. I hate the argument that girls are weaker therefore shouldn't be hit back. If your dumb enough to hit someone to hit somwone who can kick your ass, the. That's on you. Anyway they both got suspended after I argued my point. Her mom was pressing charges and so am I. Cause she broke his nose. I did tell him he shouldn't have hit ANYONE with a chain. You tell a teacher or someone, do not resort to violence with ANYBODY if it can be avoided and he just started crying because I know he finally just snapped and was over a lot of the bullying and if I could switch him schools I would.

Edit: Oh I have everything! Even the surveillance video of that group coming up to him and her kicking him. I've got everything for court. I am suing