CNN story
here, very sorry but it's video only.
The gist of it is, some schools are abandoning their new healthy lunch initiatives that encourage less fat, less sodium, and (*gasp*) fresh fruits and vegetables in the cafeteria. The story focuses on the idea that it's because the kids don't like the meals, and aren't eating them, but they sort of slide past why this is actually a problem for administrators.
It's because the schools make money off their cafeterias. Put good food in the cafeteria, and some kids are going to start bringing their shit from home instead, and that translates to a loss of money for the school. It's why schools love their junk food vending machines, and their Taco Bell kiosks in the cafeteria, and generally won't remove them until legislation requires it. Because that's what sells, and thus ensures they have textbooks for another year.
Fund the schools well enough, and they wouldn't be whoring themselves out to the lowest common denominator.
Ironically, I've always been hurriedly encouraged to send my own kids' lunches from home. Because legally, all I need is a doctor's note and I could actually demand that the school feed my children on their medically-necessary diet in the cafeteria. I never would of course, because duh. But every once in awhile a staff member will start upselling the great cafeteria food to me, before their coworkers start giving them dirty looks and shaking their heads no.