They increase the overall rate of transmission, putting everybody they're in contact with at greater risk. Especially since they're in schools, often in close contact with multiple cohorts per day. Diseases spread most quickly through densely-connected social networks. We didn't see significant transmission in children with the early variants, but with Delta, the game has changed.

Risk of what? Who cares if people catch covid. It’s never going away. Covid is here forever. Get your vaccine and move on. Vaccines work.

The people who catch it care. The people with dead relatives especially care. The hospitals full beyond capacity care. The patients denied treatment because hospitals are overloaded care. The health care professionals who are overworked and have PTSD from working under these conditions care. Not everybody has, or even can, get a vaccine. For those people, and because of those people, masks are used.