For a black and white semi formal dance use black lights. Try hand outs (have them buy cheap things provided by the school, like glow sticks, or just something that will make a statement in the black light.)
To make a gym "shrink" you might try taking up space with props, the DJ or the photos. You could set up a wall somehow to block off the dancing so it is like having two rooms
Login using the form on the top of the page to post feedback (if you are a registered user). If you have not yet registered, click here to do so. It's FREE!.