But what if the Delta variant makes kids sicker? Or if the Israeli study is right and the Pfizer vaccine is significantly less effective against it, raising the likelihood of vaccinated teachers getting sick? The fatality of the disease might remain relatively low for exposed teachers. But tests revealing widespread presence of the virus in schools could inspire panic among anxious parents — and within teachers unions. Teachers in many school districts around the country have a track record now of prioritizing their own health and safety in the face of an uncertain epidemiological threat over the developmental — intellectual and social — needs of the nation's children. Will they make the same calculation if case numbers are surging again as we approach Labor Day? I certainly hope not. The Biden administration as well as state and local officials around the country should be doing everything in their powers to ensure that all kids can return to something resembling normal schooling this fall. That means making vaccination against COVID a requirement for attendance for all kids older than 12 — and moving mountains to get the vaccines approved for younger kids in time for such a mandate to be universally enforceable before the start of the school year. We already require shots for measles, mumps, rubella, tetanus, diphtheria, polio, and other diseases. Adding one more wouldn't be onerous or unreasonable, and it would do a world of good. Beyond that, it just might be necessary for Americans to adjust their expectations around risk.