I have had students think about what the coolest music would sound like, and try to sing a phrase which I write down, then another and another. Most of the time students will come up with some that makes complete sense that is creative and interesting and beautiful. If we could only tap into that uninhibited creativity and always write exactly what we want.
Every student learns and develops in their own way. There is so much great music out there, if a student isn't motivated to practice they haven't found the right music.
Kids are born with natural instincts and musical ability that should be nurtured only to guide them through.