For lunch boxes, get a gel pack.

Basically, an ice pack is frozen water and a gel pack is frozen gel—and for lunches, the gel pack is the one you want.

Ice packs are just water in a plastic shell. Freeze them and they get hard as a brick, which is fine for a cooler but awkward for fitting around a sandwich. They also sweat like crazy when warm, turning your lunchbox into a puddle.

Gel packs have a water-based gel that stays flexible even fully frozen, so they bend around a juice box and don’t leave puddles. The gel also freezes at a slightly lower temperature, so it stays cold a bit longer outside the freezer—exactly what you need between 7am and noon.

The downside: gel packs cost more, and if punctured, the stuff inside isn’t food. But for everyday lunch duty, that’s a fair trade. Your kid won’t notice the difference, but your lunch bag will.