Boy won’t stop touching me !

I don’t really know how to say this but there’s this boy who I to be honest hate and ever since this joke was made in my history class he had started calling me really racist names and stuff but recently it’s got to the stage where in mainly history (I sit next to him in more classes it just happens more then since I sit at an all boy table 3 boys then me) he has started touching me it started with a pencil like poking my back but then he started touching my hair and running his fingers down my back and I tell him to stop and he doesn’t when I go into my history class I feel really uncomfortable and quite scared I have told a friend when it first happened because I was quite freaked out but whenever I tell him to stop he keeps going probably because his friends are there the only time one of them has intervened was when he touched my hair and that was the only time anyway we go back to school soon and don’t know if I can cope with it again just need some help ?