Are you calling for a single round of testing?

 More on Reopening Schools No. To keep schools safe, one must commit to frequent retests. Even if hypothetically one could get to the point where no one in a school was infected, some students or staff members will be infected by interactions outside of school. Depending on the prevalence of the virus in the surrounding community and how safe the community wants schools to be, one could test once a day, three times a week, once a week, once every two weeks, ...

What happens when someone tests positive?

They have to go into isolation. After two or three weeks, they will no longer be infectious and can return to the school.

Will testing make sure that no one ever gets infected at school?

No. The right level of testing can reduce the risk of an infection by the same amount as a six-foot separation would, but neither will deliver zero infections at school. To illustrate this point, imagine you have a classroom that has so much space that you can move the desks so they are all six feet apart without removing any from the room. According to a recent [review article](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext), a separation of 2 meters implies a four-fold reduction in the risk of infection. This estimate is based mainly on evidence from encounters in hospitals and may overstate the advantage of distance. In a poorly ventilated classroom, the smallest "aerosol" droplets will diffuse over a much wider area. But for the purpose at hand, take a four-fold reduction in risk of infection as the goal. Instead of reaching it by enforcing the 2 meter separation, a school could test frequently enough to reduce by a factor of four the probability that an infected student is in a classroom.

What's the advantage of tests over distance as a way to get a reduction in the risk of infection?

The problem with distance is that there isn't enough room to move the desks 6 feet apart unless you remove many of them from the classroom. This means that a school has to find a way to keep most students away from the classroom most of the time. The schools claim that they can still teach the ones who are not in the classroom by relying on remote instruction, but the evidence shows that this type of instruction does not work as well. The figure below shows how student progress in math slowed when the pandemic forced a switch to remote learning. {{< figure src="chart.png" title="" >}} This second figure shows that students from poor families suffered the most from the switch to remote instruction. {{< figure src="chart2.png" title="" >}} If the Congress pays for tests that keep schools safe, this cost is shared among current taxpayers. If schools follow the CDC guidance to keep schools safe, the cost is borne by the students. Because they learn less, they have lower lifetime income. Because the effects are concentrated on students from poor families, following the CDC guidance will increase inequality and reduce intergenerational income mobility. Finally, because the return on investment in human capital is very high, the CDC approach is, in effect, a tax on the future income of students that imposes a high deadweight burden.