My son was physically ualted at school where do I go from here?

A year 10 student ualted my child (year 7). He grabbed him by the throat and threw him to the floor, was pulled off by a female teacher. She wasn't strong enough to hold him so he then tried to strangle my son again. What are my rights as a parent? obviously the school are involved but I would like to know a bit more before I attend a meeting. This was a totally unprovoked attack.