Someone please help!!! Very serious. I'm being physically aulted at school? :'(?

I'm in high school and every day of the week I have gym cl each morning. I'm a 16 year old kid suffering from autism and there are about 23 other guys in our cl and only 2 girls. We play "Sand Man Ball" every day in a mini gym and it gets real brutal. I don't want to play with any of the guys because they all play too rough and some of them hurt me on purpose by throwing rubber straight at my face and it really hurts. There is this one guy named Mike and he always wants to see dark bruises on my face. He's the one who mostly targets me by throwing any ball he has in his hand at my face. So I ask him why he wants to hurt me and he says "because you're a f****** retard so you deserve to get beaten good". Then he punched me in the face. There is no way I can defend myself because he is by far a lot more stronger than me. After cl I try telling my instructor what Mike and the other boys do but she does nothing about it. So afterwards as I'm showering naked in the boy's locker room getting ready to go to my next cl, Mike all of a sudden comes over to me pushes me to the ground. Then he takes his thing out and starts putting his you know what in my ocks calling his other friends to come and watch shouting at me not to move :( I started to say to Mike to please stop, but he laughed and refused to. After he aulted me, Mike whispered at me "See you tomorrow retard", then they all left and I was laying there not knowing what to do next. When I finally got up, I knew right away that if I went and told the vice-principal or principal then they would not believe me or do anything about it. I tried at times to tell the school admins but they did nothing. I knew I could not go to my next class so I decided to leave the school and call for help. I can't go to my parents because they are at work. Who should I turn to for help? I need someone who will believe me.