Jamie Oliver has done this before, in England. He encountered a lot of the same problems and naysayers there, but perservered, and convinced the British government to make significant changes to the school menus.
I really don't believe that fast food and processed food is that much cheaper than buying good fresh food; if you can cook, you can make inexpensive meals using nutritious ingredients. I agree that it's hard if there isn't the availability of the fresh food, but the sight of kids eating salt laden fatty chicken nuggets and nary a green veggie in sight is heart breaking.