Brightly colored and patterned plastic lunch bags and boxes may appeal to kids, but they often contain high levels of lead and other toxins and can be nearly impossible to clean (been there and tried that—yuck!).
Better: Choose a reusable, washable lunch sack made from either cotton or nylon, and toss it in the machine every weekend. Pack a small cloth napkin and reusable silverware, and you are ready to dine in style.
If you don't have access to a refrigerator at work or school, frozen ice packs inside a vinyl-free insulated bag might help keep perishables cold, but test it out first. Pack a jar of cold water in the bag along with the ice pack, seal it, and let it sit at room temperature for however many hours it will sit out between packing it and lunchtime. Then open the bag and take the water's temperature. If the water is warmer than about 45 degrees, test again with two frozen ice packs, or just plan on packing only room-temperature-safe foods.