I have to throw in another vote for the metal thermoses. Thermos makes 'Funtainers' that have everything from soccer balls to Batman to Bratz. They make a bottle with a straw for drinks, a wide-mouth jar for soups & such & a small 'Snak Jar' that's suppose to be for cold foods only (its non-microwaveable). My kids each have the straw Funtainers & they keep drinks cold very well. We took them to an outdoor family reunion (TX in August) & they kept their water cold.
I've had no problems with keeping food hot a/o cold. Keep in mind that with staggered lunch times, lunch can be as early as 11am & as late as 1pm. I usually pack the night before & put the lunchbox in the fridge. DH puts a cold pack in them in the AM (He takes the kids to school). I do try & cluster the hot & cold stuff so the cold pack is touching as many of the cold things as possible.
I've had no problems with keeping food hot a/o cold. Keep in mind that with staggered lunch times, lunch can be as early as 11am & as late as 1pm. I usually pack the night before & put the lunchbox in the fridge. DH puts a cold pack in them in the AM (He takes the kids to school). I do try & cluster the hot & cold stuff so the cold pack is touching as many of the cold things as possible.