Maybe he just isn't confident?

He came in to class, looked at you. He started to pull out the chair right across from you (he usually sits a few seats down) and it seemed like he was going to sit there. He said something quietly, but you couldn't hear, so you asked him what he said, but by that time, he had already moved to his usual seat.
Maybe he just thinks you don't like him?

making progress

• he asks (still not really looking at you) if you (and he actually says your name) won't join his group, the one you were part of.
• in case you didn't understand, he actually said "Hi," said your name, and asked if you would not join the group.

more signs that he likes you.

at least likes you more than normal friends that are girls. but then I really haven't seen him with any of his friends. That's not good - I still don't know who his friends are. But I do know that he doesn't do that to the other girl in the group.

• he makes sure you say bye, replying to his "see you."
• maybe the reason why he tries to get out of class as soon as possible is because he thinks you don't like him, same as you do when you have to talk to him.
• like you talk to mostly that girl, hoping he'll hear, he mostly talks to her. Maybe he thinks you'll hear.

signs that he just thinks of you as a friend

• he says says "well, happy birthday for tomorrow'' when he hears you reply to someone that "it's tomorrow" when they say happy birthday.
• he says happy birthday again as he's leaving, smiling.
• he doesn't lose composure when you start start talking about that guy, and instead, actively listens, even when you thought no one was listening.