How the US lets hot school days sabotage learning

New research shows American students are losing huge chunks of learning to heat. Here's how your district fares

Human bodies react swiftly when they overheat.

Blood rushes to the skin, trying to find cool air. Sweat seeps out of the skin and evaporates, dissipating body heat. But these processes have a cost: they reduce blood circulation, which means our most important organ, the brain, gets less blood.