how can i sue a school bus driver?

Two my kids came home on 2/25/15 crying that they was injury on theirs school bus coming home 2/25/14.My stated that she was in her seat when the bus driver personal slammed on brakes causing her to knocked her for head into back on the bus seat that caused her an knot on her for head.My son was crying as well saying when the bus driver personal slammed on brakes his whole left side of his face slammed against the back on the bus seat causing he complaint of his left ear hurting badly.I than called the school to informed them of what had happen on the bus and someon one from school said it's nothing that they can't do about it because it happen on the bus and not on school ground an I would have to call the school bus company..I advid them that my kid's as well as others kids gotten jury on bus not just one time but numerous time since school started.I than reached out to school bus company that to reach the bus driver supervisor but that was unsuccessful.I emailed an hotline to file