What is he thinking?

He's doing all the right things when it comes to flirting. Don't judge a book by its cover. I would make an effort to get to know him. Why don't you sit next to him in cl (if you can) and talk to him. if you can't sit next to him, at least try to say something to him. Small talk... like compliment something he has or talk about school. Get to know him some. It's pretty obvious that he's flirting with you. The only way to know for sure is to flirt back and see where that goes. Just be careful if he has a "player" reputation... but judge him yourself, not by other people's opinions or what he looks like.