Getting kids to eat lunchbox food

On Fridays, I volunteer to help with lunch at my daughter's school. At 11 a.m. the kids storm into the cafeteria, throw open their lunch boxes, take a bite or two out of their sandwiches, nibble on a carrot, possibly pop a strawberry into their mouths, maybe think to open their water bottle — and then rush off to recess. I stand over the compost bin and the garbage can and help kids sort their waste — lunches beautifully prepared by their parents. It's shocking. Once a little girl opened a Ziploc bag, ready to toss five perfectly plump strawberries into the compost. "Aren't you going to eat those?" "Nah." I insisted that she eat at least one and she bit the tip off the end of a berry. Some kids put their uneaten food back in their boxes but many toss their tuna sandwiches, sushi rolls, bags of chips, bananas, crackers, cheese sticks, apples. My own daughter typically leaves her peanut butter sandwich untouched. I tell her to put it back in the box, even though I knew it will be rock-hard by day's end. Many of the kids purchase school lunches and those also remain uneaten — except for the cartons of milk and the sliced oranges. Kids suck up their milk and stick orange slices in their mouths over their teeth and make funny faces at one another. Teachers and parents walk around encouraging kids to eat their food and help them open their Gogurts and Lunchables. The principal slices kids' oranges. If it weren't for them practically nothing would be eaten. I once commented on the waste to the lady who oversees lunch duty and she agreed that it's terribly upsetting. "I've thought about getting a pig for the school," she said. "That way we could feed all of this waste to him." And of course, I now have a vision of converting a section of the playground into a farm... What's the solution? How do we get our kids to eat their lunches? Are we putting too much food into their lunch boxes?