For NYT Opinion, Yaryna Serkez and Stuart A. Thompson estimated where we’re ready:
Our analysis considers two main things: the rate of new infections in a county and the county’s testing capabilities. We used guidelines from the Harvard Global Health Institute, which proposed a variety of ways to open schools as long as the county has fewer than 25 cases of Covid-19 per 100,000 people. We also used the World Health Organization’s proposal to open only if fewer than 5 percent of all those who are tested for the virus over a two-week period actually have it.
The second part matters because if a higher proportion of people are testing positive, it could mean that not enough tests are being conducted to adequately measure the spread.
As you might expect, based on these guidelines, reopening in some places and not others poses disparities when you start breaking down demographics.