Well, theres two things. If your going to a formal all school dance; wear a regular shirt and jeans (or shorts depending on the weather) As for something like an 8th grade graduation dance; DONT DONT...
You should probably wear eyeliner, eyeshadow, mascara, lip gloss/stick, and foundation. This is all depending on what you look like. I would suggest something slightly bolder then your normal...
I think you should wear like a sweet but yet spicy type dress for a girl, but for a boy, you should probably just stick with the usual, a suite and a tie or bowtie