Send an e-mail to the address on the musicians website, and if they give you permission, cool, and if they decline then scrap it.
If they don't reply, at least you made an effort, and it's your call what to do after that point. Give them credit though, if you do decide to use it no matter what unless they say NO.
We wrote an e-mail to
Hoobastank a few years back to use part of their song as a flash intro.
They agreed to let us use a snippet of the song
Crawling In The Dark as long as we credited them which we agreed to.
Most bands/musicians won't have a problem, but make sure your e-mail to them sounds as professional as you can sound.
Makes them feel better if it's going to help a HS organization, rather than a corporation as well, so mention that.
Most bands who want money for their music's use, know that whoever is using their song is making money.
That said, since most teams are non-profit (in one way or another, officially, or just the fact you are a HS team) they have no problem letting you use their tunes for free). So, make note of that in your e-mail as well.
Good luck!