Aside: Is the pink nail polish part of the uniform I wonder?
I was shooting a school dance festival in very poor light recently. No interior lighting at all: the only illumination coming from some small windows high up in one wall.
No problems with using flash for me luckily. And though I hate on camera flash is was the only option I could see.
I'm not too displeased with the results. The flash is a bit more obvious than I would have liked in some of them, but fills just fine in others.
A few samples at:
Dance - a set on Flickr