The number of schools resuming in-person instruction continues to grow, as the U.S. ramps up its vaccination campaign and daily coronavirus cases continue to decline.

As of mid-March, about half of U.S. students are attending traditional in-person school every day, and about 30 percent are participating in some face-to-face learning through a hybrid model, according to Burbio, a website that tracks school reopening trends.

Just 21 percent of students remain in virtual-only learning settings, and that rate has been falling steadily since it reached 55 percent in early January, when U.S. coronavirus cases were at an all-time high.

But a growing body of evidence indicates that it is safe for schools—including the hold-outs, which are concentrated in states such as California, Maryland and Oregon—to reopen for face-to-face instruction, granted they have the proper health and safety protocols in place.

A recent report examined nearly 130 studies on school reopening and coronavirus transmission to understand what lessons can be learned and what conclusions drawn after a full year of the pandemic.

The report was authored by John Bailey, a policy expert at the conservative think-tank the American Enterprise Institute, with support from the Center for Reinventing Public Education (CRPE) at the University of Washington, Opportunity Labs, United States of Care, COVID Collaborative and the Walton Family Foundation.

The findings in the report do not represent altogether new ideas or implications. Rather, they reinforce the message that a growing chorus of experts have communicated in recent months: That it is safe to conduct teaching and learning face-to-face, under the right conditions.

Here are the major findings of the analysis:

  • Children represent a small proportion of diagnosed COVID-19 cases. When children do contract the illness, their symptoms are less severe and their mortality rate is lower than individuals in other age groups.
  • Attending school in-person does not increase a child’s risk of contracting COVID-19, especially if protocols such as physical distancing, mask-wearing and regular sanitizing are followed.
  • Schools do not typically drive community transmission of the virus. Rather, school-based transmission tends to reflect community transmission.
  • High school students are more likely than younger students to spread the virus.
  • Schools can mitigate risk of infection for students and staff when they adhere to health protocols such as mask-wearing, physical distancing, improved ventilation and other disinfection measures .
  • The public health benefit of keeping school buildings closed should be measured against the potential academic, social and emotional harm—some of which is long-lasting—that may come from it.
  • Children face greater health risks from food insecurity, mental health challenges, housing insecurity and skipped medical appointments than from COVID-19.
  • Unrealized education and learning will have long-term consequences for students, particularly low-income students and students of color, including lower future earning potential.

“Closing schools should be a last resort and done only after every other community mitigation strategy has been deployed,” Bailey said during a recent call with reporters.

Dr. Mario Ramirez, managing director at Opportunity Labs and an emergency room physician, noted one point that’s been lost in the last year is why schools were closed in the first place.

“When we really started talking about closing and social distancing, all of those things initially were about trying not to surge the health system,” Ramirez said on the same press call. “As we got more into this, it became less about health infrastructure and much more about other things. As cases have come down and our health capacity has increased, I do think we can reopen schools.”

Emily Oster, professor of economics at Brown University and creator of the COVID-19 Response Dashboard, added that data from schools all over the country are reflected in the studies, including schools in many states that have so far resisted reopening for in-person instruction.

“Private parochial schools have been open in almost all the districts where public schools are closed,” she said. “We know from experience it’s possible to have schools open safely.”

Take Chicago, for example. While Chicago Public Schools remained fully remote at the start of the 2020-21 school year, Chicago Archdiocese, the biggest Catholic school system in the U.S., opted to reopen its 91 schools to nearly 20,000 students and 2,750 staff. The Archdiocese schools followed strict COVID-19 health protocols, including mandatory mask-wearing, daily on-site temperature checks and quarantine cohorts when a positive case was identified.

The Chicago Department of Public Health analyzed data from the first seven weeks of the new school year and found that the “attack rate” among students at Archdiocese schools was 0.2 percent, compared to 0.4 percent of all Chicago children during the same time period. The attack rate for school staff was 0.5 percent, compared to 0.7 percent of adults in the city. The local health department concluded that “implementation of layered mitigation strategies creates a low- but not zero-risk environment for in-person learning in public schools.”

Earlier this year, Chicago’s teachers union battled the city for weeks over safety measures, including teacher vaccination timelines, maintaining six feet of social distancing and improving ventilation in classrooms. The district is still rolling out its reopening plans.

Jesus Jara, superintendent of Nevada’s Clark County School District, which encompasses Las Vegas, said his was among the last districts to close last March.

“I understood [the risks], but my students rely on school—not just for academics, but because of food insecurity,” he told reporters. “Almost 70 percent of my students eat breakfast and lunch at school.”

He described families later being evicted from their homes, and students who were expected to join their live class meeting from a parking lot. He also noted that his district has lost 23 children to suicide so far this year, compared to nine the prior school year. He believes the pandemic—and the isolation and hopelessness it has brought many children—was a factor.

“I do have adults—my employees—who are susceptible to the virus,” he said. “But I have 310,000 children who need school.”

Jara decided to do a phased reopening of school buildings beginning March 1. Instead of the six feet of physical distancing many people have come to know and observe, Clark County is doing three feet of distancing.

That may actually not matter, said Oster. Experts had previously understood six feet to be “crucial” to prevent the spread of the virus between individuals, she said, but a study in Massachusetts, where school districts were allowed to choose either three- or six-feet distancing in classrooms, found that transmission rates were virtually the same in both.

A study published last week in the journal Clinical Infectious Diseases looked at the effectiveness of three feet versus six feet of distancing in 251 school districts and found that three feet would be sufficient, so long as mask-wearing and other safety measures were in place. There was no negative impact on student or staff safety in districts that used three feet as the standard.

If widely accepted and adopted, three-feet distancing would potentially allow more schools to move from hybrid (part-time remote, part-time in-person) learning models to full-time in-person learning.