I say meatloaf. I have never had good meatloaf from a school cafeteria. It always looks like slime. Meatloaf day always seems to be the day everyone brings their lunch from home.
I think most of the obesity problems come from lack of activity. When I was in school (way back in the stone age) we would have a "fun" food on Friday, like pizza or a hamburger. We had very few obese children when I was in school. Don't get me wrong, I think a healthy diet is very important, but never letting a child have a little bag of chips (like Fritos or SunChips when they serve chili) is going to make the kids go nuts for chips when they are old enough to go out and buy their own food. Just use common sense and moderation.