This boy at my schools keeps intimidating me everyone time he sees me?

It all started when he was picking on my friend so i told him to leave her alone. He is like 6ft and year above us and then every time he sees me in the corridor he pulls faces at me, shouts things at me and actually once made a racial comment about me. Also on the bus he tries tripping me up and always embarres me when he is with his friends. What can I do so doesn't hle me again? And I don't want to tell a teacher because I already told the school he said something racist to me and they didn't really do much.