Where to make female friends if you go to single-sex school?

Might be a weird question, but I go to an all-boys school so it's a little tough meeting girls. I tend to find it weird approaching girls in the places I go to regularly like the gym, library, or doing volunteer work. I'm not looking for a relationship just more so trying to meet new people and not end up being an anti-social hermit who can't talk to girls to save his life. I have been invited to parties but that's not really something that interests me. What's the best way to make female friends?