I'd request a meeting with the principal, attorney present, to discuss their bullying policies...
Watch them crabbing. Meeting is NEVER going to happen.
It's too early for the attorney. But, a few minutes with the principal, mostly low keyed can get you on the right track if there is a mutual agreement about future behavior of the other young man. Especially if the principal knows the other kid on a first name basis because of his behavior. I will bet you the principal has had it up to his/her ears with the kid and his parents.
IN private he/she is cheering your son on. Don't go in and blow it. Now is your chance to score some points with the principal and an attorney will fugg that up in a New York minute. I have seen it before.
Don't be that other parent.
kwg