I'm 12 and in 7th grade and my friend (a boy) keeps smilesing at me and looking at me in class. If he being friendly or does he feel sparks? (cuz I sure do... )

Get in his personal space (Google it) and see if he backs away. If not, odds are good. Also, does he smile at just you or everybody? Hmmm, given your age, may also want to check to see if you have a "kick me" sign or some other nonsense stuck on you.

I agree with Scleros, get to talking to him, ask him if he'd like to see a movie, or hang out at the mall sometime. If he accepts, your chances are good. :)
There are two reasons he smiles at you:
One, he's friendly and smiles at everyone.
Two, he's interested in you, so smile back.

Good luck! :)