I am soooo embarassed of my ex!?

I'm in highscool so I have to be around my ex all the time and I am just sooo embarassed that I was ever associated with him! Whenever anyone says something he always adds on the end "or is it?" and thinks he's really funny, and him and his group of friends sit around in public places and sing really loud or clap back in forth. And they say things like "Wait a mo" or "a'ight" even though they're the whitest most suburban kids around. I know I should let him be himself, but a lot of people at my school know me only by my relationship with him and I don't want to be associated with any of the socially awkward and annoying things he does. What do I do to differentiate myself from him?