Why does my teacher behave like this?

If your saying you think he is trying to hit on you, that might be possible. Ask your friends that know him as well if he likes to give them hugs. If he does, he is just a huggy person. Another reason why he would be staring at you (other than him liking you) is that he might be waiting for you to say something. But I have to say that you should probably stay away from him hun.