Heather - I know you said that kids won't eat something healthy and just won't buy lunch. That is somewhat true. My high school got rid of the old meat/potatoes/veggie/dessert lunch because half of it was ending up in the garbage and went to an all a la carte menu. They had many varieties of pizza, stromboli, a salad bar, taco bar etc. and it was much more expensive so the kids only bought what they would actually eat. Maybe we didn't get the minimum RDA of every single vitamin, but it was better than McDonald's overprocessed garbage. At least it was prepared by our friendly lunch ladies on the premises.
This is what happened when a school district around here sent out letters telling parents their kidlets were obese.
And there was a story on the news about how some elementary schools only have 10 minutes of recess a day. The kids are pretty much chained to their desks and the school is not promoting exercise at all. I'm not saying recess will make fat kids skinny, but it is definitely a factor.