Updated: Nov 16, 2019
My son isn't old enough to partake in his school's hot lunch yet. This means we are still packing his lunch for him 5 days a week. His preschool would warm lunches for the kids and so we never had to think about keeping lunch hot. His current school doesn't offer microwaving services and there are limited choices for cold lunch. Let's be honest, there are days that hot pasta or hot stew just sound really good for lunch.
We tried over a dozen thermal food containers to see which would actually keep his lunch hot. The one that came out on top was the Hydro Flask brand.
We don't have scientific measurements as to how hot the food stays, but my little says he has to blow on his pasta, 5 hours after it's been packed into the container. And that's as good as right off the stove for me.