super stressed out and feeling pretty useless..

Hi everyone... i was hoping for some advice or just a bit of general chat about what to do and how to help my son with autism. he is in reception in a main stream school and as much as he does learn in his own way his behaviour and understanding of things seems kind of out of control. its either his way or the highway and i know that is something with a lot of autistic kids, but his rage is terrible. punches, head butts pushes and scratches, throws himself on the floor screeching and screaming, he does this at home and school but he is worse in school. he has a one to one who is lovely but i find myself feeling so sorry for her at times. i am just at a loss on what to do really. there has been mention of special needs school, but i really want him to be able to keep up at mainstream if he can, and even excel. does anyone know if aggressive behaviour comes and goes with autism or does it get worse?? please help! any advice is so welcome! thankyou