Can a girl ask a guy to prom?

So, I know it's a little early to be asking about prom, but I know the hype is going to start sooner than I think and I want to be prepared. In my school we just have a senior prom, and I was wondering what people think the etiquette is for girls asking guys. I know that it's acceptable for a senior girl to ask a younger (or older) guy, or a guy who doesn't go to the school. But what's the etiquette for a senior girl asking another senior guy who goes to the school? When it's between seniors is the guy supposed to ask or does it not matter? I'm wondering because I'd love to have a traditional date, instead of just taking a girlfriend (which would be okay, but it's not ideal) but I'm afraid I won't get asked by someone I like. I was thinking of asking my ex-boyfriend with whom I'm still friends, because I'm not sure what the chances are he'd end up going with someone else. Would it be okay to ask him or would it be weird because I'm a girl?

Thanks!