Christakis' Yale lab normally studies how humans spread everything from ideas to behaviors to germs, but he says he's now all-in on studying how coronavirus might spread. Aside from developing a vaccine and getting everyone to wash their hands thoroughly, closing schools is one of the most effective things a community can do to slow contagion, says Christakis, author of Blueprint: The Evolutionary Origins of a Good Society. But timing matters. He points to studies of the 1918 Spanish flu, which suggest some cities may have saved lives by deciding to close schools earlier.
"Closing the schools before anyone in the schools is sick is a very difficult thing to do," Christakis acknowledges, "even though it's probably extremely beneficial and much wiser."
Marco Ajelli is a computational epidemiologist at the Bruno Kessler Foundation in Italy. He uses advanced math to model the course of disease outbreaks, and he has studied school closures. Ajelli echoes Christakis, saying that "there is scientific evidence" that closing schools can buy time and delay the peak of an epidemic. "And it's really important to gain time at the moment," he says, "because if you have a lot of people that get infected all at the same time, the hospitals and ICUs have not enough hospital beds."
But this understanding is based on the science of previous diseases. Ajelli and his colleagues point out that there's something new and different about COVID-19, namely that children appear to be less vulnerable to it. And it isn't clear how that fact could affect the usefulness of school closures.
The fact remains that canceling school is a difficult decision because no one knows better than educators just how much some children depend on the support they get there.
"For a large number of our students, the safest place for them to be is actually in school," says Sonja Santelises, CEO of Baltimore City Public Schools. That's why, she says, she resists canceling school because of weather, too. "It gets me some angry emails during snowstorms and inclement weather. ... I will just tell you, our mantra continues to be: Closing schools is a last resort."
One big concern for school leaders is that many kids would be going home to empty households.
"Yeah, I think that's the hardest contemplation for our districts," says Chris Reykdal, the superintendent of public instruction for Washington state, which has been hit hard by coronavirus. He's concerned about sending "a million Washington kids home knowing that for hundreds of thousands of them, they simply will not have any parents at home."
Reykdal says that when his schools take a snow day, parents can sometimes make do for a day or two, either taking the time off or working from home. But coronavirus isn't snow, and there's no way to know how long schools would have to close. Many employers may continue to require employees to come to work. (Think about the children of health care workers.) And without government intervention, which is on the table, many low-wage workers won't be able to afford to stay home.
There's a further problem here: The effectiveness of school closures is based on the premise that kids stay home with their families and limit other contacts. Ajelli points out that if parents "regroup" children to meet child care needs or if teens congregate freely outside school, the closure won't be as effective.
One more big reason school leaders are so reluctant to close schools: Not only will many kids go home to no parents, but they also may not have ample food, either.
"Food insecurity is a real challenge in our community, even without an emergency," says Alberto Carvalho, head of Miami-Dade County Public Schools. He says roughly three-quarters of his students live at or below the poverty level. Those children are among the nearly 30 million U.S. students who depend on schools' free and reduced-price meals for lunch, breakfast, snacks and, in some cases, dinner.
In Miami, Carvalho says, students will continue to eat — even if school is canceled. Food will be distributed at schools, similar to summer meal programs, or, if need be, the food can be taken out into the community.
And food insecurity isn't just a city problem, says Jillian Balow, Wyoming's state superintendent of public instruction. Many of her students live in remote, rural communities and have to spend an hour or more on a bus just to get to school. Balow says her districts are thinking of ways that schools could potentially transport bags of food out to these students in case of cancellation.
"In a worst-case scenario, we have many Wyoming [school districts] that are rural that could look to local [food] producers for an additional food source if needed," Balow says.
In Baltimore, Santelises says her schools often send kids home on the weekend with a supplementary backpack full of food. She says the district could do something similar in the event of a coronavirus school closure, though "that only typically gets a family through a weekend. So we have other ideas, we're just trying to see whether they will work in the current context."
Schools also offer a safe place for the 1.5 million U.S. kids who are housing-insecure, and in some cases, they provide medical care, dental care and even laundry services. It's unclear how schools would continue those services in the event of closures.
Beyond the basic public health risks that vulnerable students face when schools close, there's one more big worry that has school leaders scrambling right now: equity.
If schools have to close for a while, superintendents want to be sure learning doesn't entirely stop. But educators have a legal obligation to make sure whatever education they do offer works for every child — and that can be expensive. In Washington state, Reykdal says some schools are exploring online learning. That means asking: How many of my students have a computer at home? Wi-Fi? What about appropriate support if they have a disability?
"Those are paramount questions for our schools," Reykdal says. "And if they can't deliver that when they choose to jump to an online model, it's unlikely they're providing a legal basis for an equitable education."
Of all the district leaders NPR spoke with, only one — Carvalho in Miami-Dade County — said he has the technology to keep kids learning, even at home.
"Enabled by a bond referendum that goes back to 2012, we have acquired in excess of 200,000 personal devices," Carvalho says. Those are laptops, tablets and smartphones that kids in need can take home if schools close.
But that kind of access is unusual.
"No, there will be no one-on-one technological option ready for every single student," says Santelises. Though that doesn't mean learning would stop for her students: She says teachers in Baltimore are putting together old-fashioned paper packets of work that they can send home.
"It's certainly not optimal," Santelises says, but it's better than nothing.
Having laptops and Wi-Fi routers to loan out doesn't solve every equity problem. "A growing body of evidence suggests that online learning works least well for our most vulnerable learners," Justin Reich, an educational technology expert at Massachusetts Institute of Technology, said on Twitter. He's recommending that public schools make up days rather than try to rely on tech-based teaching.
Moreover, some students with disabilities need specialized, one-on-one support. This help isn't optional; it's protected by federal law.
"And this is where it really gets complicated," Reykdal says. "How does a paraeducator get to their 20 or 30 students in their caseload if they're distributed all in their individual homes, trying to dial in online? It makes the bar for universal online learning very difficult to meet."