The restrictions in Denmark and Germany for schoolchildren are elaborate and inventive. We should be working on something similar here. The size of the country is a red herring, as these are local actions overseen by local schools. Of course I would put my kids in schools with these kinds of safeguards. Children need school.
And remember, our goal is not to prevent all transmission of the virus, only to keep the transmission rate low. Some transmission is unavoidable, so we have to be smart, not mindlessly strict.