What could his strange actions towards me mean?

I'm a straight guy, and in high school. There's a guy who I've known a few years that is in some of my classes and his actions confuse me. He's one of the jock types of guys; very athletic, loves sports, and at first wouldn't appear to be gay at all, but in my presence he is the total opposite of this. When he is with his other jock friends he will totally ignore me and then when they are not in the room, and I am, he changes totally. A couple time's he has reached over, put his hand on and gripped my thigh, and then gazed into my eyes when I looked over at him. He has also reached over and randomly touched my butt. Many days he will walk up to me and do something that he knows will make me notice, I'll look up, and he'll try and make eye contact with me. Other times he will just try to fool around with me playfully.

Is he trying to send me a message, is this some strange sense of humor, or is he just being a jerk?