Don't mess around with going to the athletic director. This needs to go to the principal, although I am willing to bet he's heard this before and nothing will come of it. He's an older teacher who has probably been doing this for a long time. If the principal doesn't remedy the situation, go up the chain of command. Every district is organized differently, so it's hard to know who to tell you to go to. There is probably an assistant superintendent in charge of student services (or somesuch title).