Harry has an invisibility cloak (it's used in all the books), so maybe have a "cloak" a child could wear and they are now "invisible" to the others they are dancing with.
However I'd avoid arming your dancing children with wands or broomsticks unless you want them all to loose an eye. Although perhaps the Harry Potter glasses could be sufficient eye protection?
Harry Potter's school has four houses:
Gryffindoor - Harry's house, brave, reckless, loud, showy, wear red.
Hufflepuff - quiet, nice, loyal, do gooders, bit of a laugh, wear yellow.
Ravenclaw - smart, geeky, serious, studious, occasionally dreamy, wear blue.
Slytherin - evil kids, wear green.
In the final book the school kids and a few parents and concerned citizens fight bad guys AKA death eaters Voldemort's lackeys, they wear black.
For the beginning part of the dance I'd stick with general school vibes, friendship vibes with the occasional fight with a scary dancer all in black, then gradually have more fights, some hiding under a cloak, then a big dance fight at the end.
If you want to show your frustration at the ridiculous homework this teacher has set, have the kids bring in a pink cardigan for the teacher to wear and tell them to stand in the back of the stage with a clipboard. This is in reference to Umbridge a rather nasty teacher and decided bad guy.