DS's orchestra checks out concert attire for both boys and girls. Boys are in tuxes (we provide the shirt, socks and shoes), girls are in long black skirts and black blouses. It's so nice that it's part of a uniformed, check out, just like any other "team". Good luck finding the skirt. They are pretty simple to make if you know someone who sews.
This happened when the chorus sat on the steps during solos and during bad and orchestra concerts. I never understood why we had "repeat offenders;" what were their parents thinking 