If your students are that good, and they arent gonna do recording, have you considered Reason? It's totally self-contained (sequencer, sampler, drum machine, synths, effects, everything's there) so you won't have to pay more for VST instruments later. Learning curve is fairly gentle at first (no steeper than Cubase SE + VST soft synths), it'll be up to your students' imagination to get as complicated as they like. Plenty of schools are teaching Reason already... actually, there's a teaching package at Reason's official site.