I think it’s entirely reasonable to believe that individual kids are more resistant to spreading COVID, but closing schools is a powerful intervention. Schools have _lots_ of kids in them, in close proximity, and _every_ child lives in a household with at least one, but on average more than one, other person.

This is not the only study implying closing schools was a sensible step:

https://www.nature.com/articles/s41562-020-01009-0