The school lunch argument is neither here nor there, but needing a 3,000 calorie per day diet doesn't mean to get most of those calories at lunch. Lunch, in fact, is supposed to be the lightest meal of the day. Properly raised kids will get the rest of the calories they need for breakfast or lunch.
That would be nice, but breakfast is limited to 600 calories and a lot of kids don't get dinner till late. Many poor kids, for whom the program was set up, rely on school lunches for most of the caloric intake. Schools used to make sure they had more than enough to eat, but not any more, so we'll have growing teens on a 1450 calorie a day diet instead of a 3,000 calorie a day diet. Thus the mass protests (some schools have seen 70% of their school-lunch kids boycott the program).
On the bright side, forced starvation is very effective at switching a person's political affiliation, so I'm glad Reagan or the Bush's didn't pull this one.