Delta does not require a complete overhaul of school mitigation strategies compared with last year. The same tools still work. “Delta may be more transmissible, but it can’t defy the laws of physics,” says Amanda Simanek, a public-health researcher at the University of Wisconsin at Milwaukee. “We have a good sense of how successful mitigations were with other variants that weren’t as transmissible. We’re going in not totally blind.” But with Delta, schools may have to add measures to reduce spread to the same level as before. “There’s no single intervention that’s the magic bullet, but a set of layered interventions can work together to stop COVID. I would say it’s still true for Delta. It’s just that you need more,” says Meagan Fitzpatrick, an infectious-disease modeler at the University of Maryland School of Medicine. For example, schools might layer on surveillance testing of students without symptoms—Baltimore has such a program, but it’s still rare in schools across the country. And vaccines for teachers and students over 12 are new tools that were unavailable last year. O’Leary told me he is “very optimistic, even with the Delta variant,” about schools that have mitigation measures in place.

The problem, however, is that many schools across the country are doing less rather than more. Nine states have passed bans on mask mandates. And with less remote learning and more kids in school this year, as well as a more transmissible variant, the United States is almost certainly going to see more cases among students than last year.

“We’re really nervous and quite disappointed,” Kendra Babitz, the COVID-19 state testing director for the Utah Department of Health, told me this week. I reached out to Babitz because Utah had pioneered a“test to stay” scheme last year, in which exposed students who tested negative on a rapid antigen test and had no symptoms were allowed to return to school instead of quarantining for 10 days. The CDC published a report highlighting the success of the program, and epidemiologists have pointed to it as a model for other schools. Utah’s legislature even passed a bill requiring “test to stay” in schools.