You should go to the Willie Mae's Music Lab Movie Night! Even if you're not in the Willie Mae Rock Camp for Girls (which is an awesome organization all about the empowerment of young girls), then you can attend the movie to find out about after-school music classes.
Girls Rock! The Movie is a documentary-style film following a group of female rockers at the Rock Camp for five days. Brian Orndorff calls it "a film not just to be commended and enjoyed, but a remarkable camp that should be a requirement for every teen girl out there in dire need of empowerment and focus."
The screening is on Thursday, July 21, 6-9 pm. It's located at 87 Irving Place, Brooklyn. To rsvp email firstname.lastname@example.org