There's a good discussion on today's episode of the Daily podcast (Feb 27). Basically the theory is that children often get the 4x regular coronavirus strains and this provides a bit of protection against the new coronavirus strain. Therefore they tend to get subacute cases of coronavirus but can still spread.

Here's an unintended consequence of closing schools though. Who often takes care of children when schools are unexpectedly closed? Grandparents. So in a way, they could be making this worse.