teaching fantasy writing

Has anyone tried teaching fantasy writing, since students, post Harry Potter, are really into fantasy writing?  I do teach a Stephen King story that has the devil appear in it but if I call that fantasy writing then a certain segment of the class feels their religion has been insulted. My argument against fantasy writing is that we only have time for short fiction in a creative writing class with 23 students, and they are not skillfull enough to set up a fantasy world in a short story without the setup overwhelming the story.  What are your thoughts?