I have a major crush on my classmate. He's also my ex. He is always my partner in school activities and reports because we have the same class number. We don't talk much. He likes another girl and I think he's courting her. I'm just confused because I always feel that he's trying to get my attention. He would always go near me, laugh loud, tell jokes, I just can't explain it. My friend also thinks that maybe he still has feelings for me. What do I do? I really get jealous when he is talking to that other girl.

If he is already an ex and has another girlfriend I think that says it all.

Don't waste your time being "around" in case his current girlfriend doesn't work out
And he can run back to you until he finds another.

Kick him to the curb, forget him and find someone you're sure likes you.
That shouldn't be something you have to guess at.
You should know it.

Well, I know how you feel. I had an ex that I was madly in love with even after our breakup. We were in saxophone together, so we'd chat a lot, and laugh. But then he got together with one of my 'best friends'. I was really mad and distraught. I moved schools because I got a scholarship somewhere else, and now I know a few other boyz. But I still did swimming there with him and he'd always tell me and ask me about his relationship with his new girfriend. I'd be there for him always, and my love for him is still there.
Maybe just being a friend who he can talk to s better than being his girlfriend. Try it out!