Can you teach someone to write music?

How do you teach someone to be creative? I've been working on a project with some 13 year olds at my school, using logic pro to write a short piece based on three or four chords and some basic rhythms. 

Having given them the important info about chords and how they relate to each other, we then got on to talking about how you develop your piece once you've worked out your chord progression, and then how to arrange different instrumental sounds to make it effective, and then how to spice it up with some funky rhythms and maybe a catchy melody.

It struck me sometime during all this that there has to be a point where the person teaching needs to just let the student 'be creative'. So where is that point? If a student's piece is all out of time, or the melody clashes with the chords, why is that not OK? There's plenty of music out there which has little sense of rhythmic or harmonic 'order'.

I guess it could be like a politics teacher trying to impose certain political views on a student. All we should be doing in composition is showing the students what successful composers of the past did, but then letting them get on with it. After all, neither Mozart or John Lennon made their name by doing exactly what someone told them to!