"Swing and Salsa are not ballroom.

Waltz, foxtrot, rhumba, cha cha etc are ballroom..."

Salsa is not ballroom, but basic 6 count swing is as much a part of ballroom as the rumba and cha cha are.

To answer the original question: teach only 2-3 moves per dance. The point of a prom is not what you are dancing, but who you are dancing with. Teach too many figures, and you can be sure there'll be no interpersonal intensity to it. Hmm, if you are from the administration you probably want to distract them with lots and lots of moves, lest they discover the joys of... eachother.