My crush is not who I thought he was?

In class he looks at me, faces me, but never talks to me. I've talked to him a few times but I've initiated the conversation every time.
I first had a crush on him because I thought he was a quiet, funny, thoughtful guy but it turns out he's loud and disrespectful, and funny in a way where he puts people down for humour. He's appeared to change over the past 3 weeks.
Just today he was talking about how another girl was the 'hottest girl in the school'. I don't know if he was trying to make me jealous but he said it right after I walked in.

So basically, I liked this guy, but he's not that person at all, and I feel frustrated and irritated because I let my grades fall a bit because I was too busy thinking about him and seeing if he likes me instead of studying.
I don't know what to do to forget about him? I don't get butterflies any more-I'm just upset... Any ideas?
My crush is not who I thought he was?
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