I have a crush on this guy. He knows and he said it was okay. We've never talked and when he first found out he didn't mind at all. But lately he's been avoiding me. When we see each other he turns around and walks away in front of me. It hurts. What do I do?

According to this he may be in some kind of problem...

I think you should ask him if he is OK and if he does not hear you try to find a way to ask him like leave him a note on his door step or if you go to school put a note in his locker

I can only guess what is going on in his mind but from your description, it does seem like he's a bit weirded out by it. I mean at first he may say that it was okay because he was flattered. Knowing that someone likes you always makes you feel good about yourself (unless this person really really really creeps you out). So since he didn't really know who you are and wasn't creeped out by you in the first place, he felt happy and good about himself.

But you saw it as a green light is my assumption and you tried getting close to him. That's when he realized that he doesn't actually want to be with you and it was his mistake for not saying so earlier. This would explain why he's starting to avoid you because he felt bad for not telling you "no" when he had the chance. Instead of facing things head on, he simply runs away which is rather cowardly but is a pretty common thing for people to do.

But like I said in the beginning, I can only guess what is going on in his head. I'm not saying that this is exactly how it is, but I'm only suggesting a likely scenario of what is really happening here. Whether or not my assumptions are true, the fact that he's avoiding you is a bad sign especially since he seemed to be okay with it at first. That's why, as hard as it is to do so, you'll have to let him go and move on. This guy is obviously not someone who is right for you to date at this moment and that's perfectly okay. Anyway, I wish you luck!