Did closing schools help? Researchers have a plan to find out

To test whether it was safe to open schools, they envision what is called rapid-cycle randomization, in which measures are quickly evaluated and adjusted as data emerge.

In the first cycle, schools in one district would remain closed while those in another would reopen carefully with, for example, half the usual number of students and with six-foot social distancing in place. Students and teachers in both districts would be tested for the coronavirus at the start and end of the cycle. Each cycle could last between 10 days and two weeks, accounting for a viral incubation period of four to five days.

If the careful reopening did not result in increased transmission of the virus, the study would advance to the second stage: Schools in one district would open with half the normal number of students and six-foot social distancing while those in the other would have three-quarters of the normal number of students and maintain just three feet of social distancing.