They won’t be.
Scaremongers are asking for schools to close for a month or two or more. Behaviouralists and public health experts have made it clear that there’s no way that all kids will stay in their homes, not meeting mates and elderly relatives for such a very long period. People would not adhere to that in a free country, advice fatigue soon kicking in.
Most of us may get the virus anyway. The plan is for shorter term school closures as and when appropriate.
In my opinion I picked it up or something massively resembling it from my son being around his friends who came back from a half term trip to Madrid. That's not scaremongering. I imagine there are more possibly only just starting to show symptoms at that school