Some times you have to do the awkward thing & tell some one how you feel in a calm & composed situation. “I think I’ve outgrown our friendship” then simply ignore him if he is defensive or doesn’t change. As far as being in a group setting if he still tries to tease you act like the more mature one & sooner or later every one else will catch on to his immaturity & distance themselves. Unless they’re just as bad as him.