I saw this, too, when I have volunteered for lunch duty at my kids' elementary school. Kids had hot lunch trays loaded up with food, but then I'd see entire salads, unopened cartons of milk, even whole unpeeled bananas tossed in the trash. I'm sure there are food safety issues that come into play that make it impossible to return the foods to the cafeteria or even to donate, but it's a shame to see food wasted like that (not to mention the parents paying for the kids' meals who think their kids are eating healthy, full meals)