The Pennsylvania Department of Education wanted to know more about the potential effects of reopening schools could have on the spread of the coronavirus, and what precautions schools could take to minimize infections.
So it asked a team of education and infectious disease researchers from Mathematica, a private company, to analyze the potential outcomes for schools over several months. The analysts looked at both the way that schools tried to reopen and how they responded to any infections. While the study focuses on Pennsylvania schools, the state has such a variety of scenarios that districts around the country can look to it for guidance, the researchers said.
“There’s nothing the school can do to control infections that occur outside. So you always have to anticipate that there’s a possibility that somebody is going to come in with an infection. So the real question, from a policy perspective, is can the school’s operation cause an increase in infection, cause infections that wouldn’t have otherwise happened?” explained Brian Gill, an education expert for Mathematica.
One of their most striking findings was that, according to the modeling, and under the right circumstances, schools could largely stop the spread of the virus in the classroom.
“If you’ve got a well-implemented hybrid [part-time in classroom, part-time online] approach with precautions, like wearing masks, and if your community infection rate is moderate or lower, then most of the infections that come in from outside are likely to lead to no additional transmission in school,” Gill said. “The school is not contributing to the problem. The school is not making the local communities and infection rate worse.”
The Mathematica team also found that hybrid models offered a lot more predictability for students’ schedules than students returning to their buildings full-time. In areas with low or moderate infection rates, in fact, students “experience little or no unplanned disruption in the days they can come to school,” the researchers found. Of course, most hybrid models assume that students only come to school two days of every week to begin with.
But things can be more volatile for students attending in-person full time, because of interruptions for quarantines when an infected student is found.
Delays in Covid-19 testing results also have more serious ramifications for schools operating on full-time in-person schedules, the researchers concluded. But faster test results had “no measurable impact” on how fast infections spread in schools using the part-time model, because infections were already low to begin with.
The goal of the study wasn’t to provide blanket recommendations for school districts, because the right call for how to schedule students this year could depend greatly on local circumstances. Gill noted, for instance, that elementary schools in communities with low infection rates might not see huge advantages for moving to hybrid instruction.
That said, Gill added, “if you’re a secondary school, if your community infection rate is moderately high, rather than low, then the hybrid approach tends to show more substantial benefits.”
Of course, the models used by the researchers are all based on scientists’ current understanding of how the virus works, which means that there may be some aspects of how covid-19 spreads that the models don’t take into account. A few months ago, in fact, the same team ran a similar (but less ambitious) exercise. At the time, though, the researchers did not know that transmission among young children was substantially lower than it was for older children. That’s now been built into the latest models.
“There’s still a lot of uncertainty about the way the virus works,” Gill explained. “And there is, I think at least as much uncertainty about the way that humans respond to these rules and restrictions in schools.”
With the school year still in its early days, for example, public health experts don’t know how well students will comply with rules to wear masks, keep six feet apart from their classmates or not interact with kids outside their pods.
And then there’s the question of how people in and out of school respond to a school’s decision to allow students on campus. One possibility is that people could erroneously see the reopening of schools as a signal that it’s safe to do risky activities that have been prohibited or restricted since the pandemic hit.
“All of this modeling assumes that schools only have control over what the kids and families do in the school. If for some reason the school’s approach caused families or kids to take additional risks outside of school, then this goes out the window,” Gill said. “If families were to respond to hybrid approaches by putting their kids into group daycare on the other days, when they’re not in school, then you’re going to undermine the benefits that you got out of reducing the contacts.”
The researchers assumed that 20 percent of students in their hybrid models would stay at home full-time, because of a vulnerable family member or other concerns. They assumed that, under that scenario, buses would be 40 percent full, rather than the 20 percent recommended by the U.S. Centers for Disease Control and Prevention. The only scenario that the researchers considered that would result in that level of reduction would be to have students only getting in-person instruction one day a week.
A copy of the report, which includes an appendix with more detailed models for schools facing different conditions, is available here