Green your school lunch: eat local.
Most produce in the United States travels an average of 1,500 miles between farm and fork--that creates a lot of transit pollution and can contribute to health problems for people living near ports. You can cut down on pollution, and the miles your food travels, by buying locally grown produce in season more often.
Also, you can reduce waste every day by packing your children's lunches (and your own) in reusable containers, and providing them with things like reusable BPA-free stainless steel water bottles rather than single serving juices or waters.
More information about what's in season and where you can find farmer's markets near you can be found with NRDC's Eat Local tool on Simple Steps.