Exactly!
We're so afraid a child might not eat that we give them a dozen choices...... Instead of saying lunch is XY & Z. Even at home, I've seen mothers get up to fix Jr. a PB&B because he's upset with meatloaf.
In controlled settings where all kids are served the same meals with the understanding there are no subsitutions outside of allergies etc, you'd be surprised how quickly they start eating their veges etc.
Heck, I've seen them take a liking to collard greens and cornbread after a bit. And that ain't expensive food.
I don't mind providing free lunches for school kids. I'd rather provide food, then give their parents money or food stamps.
However, it could just be something simple: a piece of fruit and a simple sandwich (peanut butter or turkey), and some milk. If kids don't like it, then they can take their own lunch to school. Also, a lunch like I mentioned will not contribute to obesity.