Your athlete needs a cooler, not a lunch box.

Most lunch boxes are built for office workers, not for a teenager who’s trying to put down 4,000 calories a day.

Capacity is everything. A standard adult lunch box holds maybe six liters — that’s one meal, not two. Your kid needs room for a real entree, a second entree, snacks, fruit, and a shake. Think 16 to 20 liters of usable space, or a stacked bento with at least four tiers.

Insulation is the second thing. That food sits in a locker from 7am to 3pm. If the bag doesn’t have thick insulation and a good seal, you’re packing spoilage, not lunch.

Durability third. It’s going to get dropped, stuffed, and thrown around. Skip anything with flimsy zippers or cute inner compartments that eat up space.

The right pick is a soft-sided cooler bag in the 20-liter range, or a four-tier bento stack. Both do the job. Just don’t buy the $15 character lunch box.

Your kid will eat more than you think. Size up.