If you like the boy, I'm guessing you've done your best to have him notice you, and you've spoken with him a bunch of times to break the ice. If you haven't, then you should.
But if the guy you like really doesn't like you back, there's only one thing to do. Let go of the dream and look for another one.
If there's not another boy in your school who catches your attention, just wait until you're old enough to go to college or university or a job where there will be a whole new bunch of guys. The fun really starts when you're an adult. So I suggest you concentrate on your studies now so you can get into university or a really good job. They're the places you're most likely to meet your life partner.