In sports, you can usually play for the school, but if you want to play outside of school, you may have troubles finding a league to play for. There are probably a couple leagues at least in the DC area, but how close to the city you're in will vary. I mean if you really wanted to play, you could drive the extra distance to go there or you may have to convince your parents to take you if you can't drive.
To find volleyball leagues in DC or any place really, just look in the newspaper, watch for flyers at school or posted around the city. When looking for volleyball leagues in DC, you may want to check out the mall courts behind the Lincoln Memorial which contains outdoor courts or the Hines recreation center that has indoor courts.
However, if you can't find any volleyball leagues in DC, and you don't want to try another sport or drive, you need to keep your skills up for the following school year. You could do some volleyball drills if you had the place for it and if you were a setter, you may want to try going to some volleyball setter camps on the off season to keep your skills good!
For more information on volleyball magazines go here!