It's good that you still talk, but if it's awkward when you guys talk you should maybe try and get to know her better before asking her out. You don't want to be stuck in the situation where you're going out but you can't talk to each other. Been there before and it's not nice.When i see her i loose the confendence to, but we still talk. :D
What if she says no? It's up to you countryemo, if you've got the guts definitely take PinkSquid's advice, but I definitely wouldn't be up for this. She might get weirded out by some guy saying "hey can you meet me here" and even if she does go and you ask her out and she says no then what? Or if she says yes, what will you do then? Think through.Can you invite her out somewhere alone? After school or during lunch? It'd be nice if you could take her to a nice spot of the school yard and ask here there or something :)