where do i go when the school system wont help me ?

my son is a mentally and physically impaired child. he was recently dropped off from the bus at our local police station. they sent word to me through my daughter who is also mentally impaired that my son was at the police station and the police would bring him home when they chose to. my son and the monitor got into a arguement where both parties was cussing and then the monitor pushed my son and he then threw a wad of paper and a pencil at the monitor.instead of the school stepping in the sub driver tok my son to the police station. wen i got there my son had urinated all over himself and has had nightmares ever since. what should i do and where should i go when the superindentant wont help and the chief of police wont take a complaint on his officer?