I would have pressed charges through the police department after the first incident, sued the family for civil rights violations, and sued the school for allowing a hostile learning environment.
Someone tried to bully my eldest in high school on the first week. One quick trip to the Vice Principal, dressed in my nicest suit, where I very calmly told them exactly what would happen if anyone touched my son after providing them the name and number of my attorney, stopped that nonsense immediately.
You mess with my kids and I will exact vengeance of biblical proportions.
Could the hospitalized kid, or friend, have called 911 while the assault qas going on? School sure did not care.