They know the deal they commit to.  Don't like it, don't play.  But I think their commitment, should actually be a commitment.  The school and fans support you, and you should do the same for them.  Jumping ship early for a chance at the Pros?  That's fine, but I think you should be responsible for whatever years you didn't play that you committed to.     
Yes, I realize there is no binding contract when a player commits, but I somewhat think there should be.