Guys in my school staring at me?

There's a random guy who's in a lot of my cles who, for most of the period, just stares at me. It's really annoying and it's kind of scary. I don't wear anything provocative or anything to make him stare at me. I'm not sure what he's thinking in that mind of his, if it's a dirty thought or arguing if he wants to talk to me or something. It kind of freaks me out knowing that tomorrow, he's going to be staring at me again and my mind is going all screwy thinking about it!