On Monday, the Cheltenham School District will reopen classrooms for the first time since emptying them almost a year ago as COVID-19 hit the area.

Though coronavirus cases are higher now than in the fall, Superintendent Wagner Marseille feels prepared. The district has consulted health experts, installed air purifiers in its oldest buildings, and watched as other communities have ushered students back into schools.

“It was fear of the unknown,” Marseille said of starting the school year online. But many schools have been in person since the fall, “and they have found ways to make it work.”

As has become commonplace during the pandemic, uncertainty abounds. Marseille was unsure enough teachers would return to work Monday to staff in-person classes, something he warned parents was a possibility as late as Friday night. And after months of students staying home, predictions of significant snowfall could make their first day back a snow day.

But more in-person schooling is coming. Marseille is among the educators buoyed by federal health officials who say data from several states and Europe indicate “little evidence that schools have contributed meaningfully to increased community transmission.”

In the Philadelphia region — where schools have welcomed back students to varying degrees, from part time to five days a week — most county health officials say there have been limited instances of the virus spreading in schools.

The Cheltenham district is one of a number expanding in-person learning in the coming weeks. Philadelphia’s school district, which hasn’t opened classrooms since March 2020, hopes to resume in-person classes in late February.

» READ MORE: A Philly private school’s attempt to get vaccines for its teachers has set off questions about equity

Evidence that students aren’t a significant vector for COVID-19 transmission is tempered by the reality that safe schooling depends on factors including students’ and teachers’ habits and the design of school buildings. Schools will still require extensive restrictions and precautions; there is some evidence that when community case rates get high enough, schools can be a significant route for transmission.

“We’re all up against this incredible hurricane,” said Wissahickon School District Superintendent James Crisfield, whose district has been teaching kindergarten through fifth-grade students in person five days a week and older students part time. “We’re standing on one foot, trying to stay balanced.”

Debate over safety

The reopening debate remains fraught as schools try to balance safety with a growing concern that many children — particularly the most vulnerable — are falling behind. Teachers’ unions in a number of communities have balked at returning to buildings, calling for vaccinations first. Maintaining proper ventilation and social distancing has proven difficult in some school buildings. Some parents have pushed for broader reopening; others are reluctant to send their children back at all.

“We do hear from parents and teachers alike on this issue,” said Herb Conaway, director of Burlington County’s health department and a state legislator. “The opinion runs the gamut from ‘Kids should have been in school yesterday’ to ‘Why is there any thought of bringing my children back in the middle of a pandemic?’ ’'

Nationally, students ages 5 to 17 account for about 9%, or almost 1.8 million, of all COVID-19 cases, according to the Centers for Disease Control and Prevention. Children and teens overwhelmingly experience mild symptoms or none at all. Youth can infect others, but apparently not as effectively as adults, a difference that has made reopening schools viable.

While “we’ve definitely seen some transmission in schools,” it has mostly occurred “at the very high end of case incidence,” said David Rubin, director of the Children’s Hospital of Philadelphia PolicyLab, which is recommending that area schools move forward with reopening plans. “It’s still more infrequent than transmission that occurred outside the school.”

Further complicating efforts to understand the risks, counties vary in how they track cases and report data.

In Philadelphia, where many private schools have been operating in person, the city has tallied nine school-related outbreaks. The health department defines a school outbreak as six or more cases among students and staff within 14 days that can’t be explained through another setting. If 5% of students or staff in a given school are infected with the virus, it’s also considered an outbreak.

In Bucks County, though, the county won’t record cases as school-related without firm evidence that people were infected in school.

That county — where most school districts have reopened in person — has no confirmed cases of in-school transmission, health department director David Damsker said. Still, he added, there were “a handful of situations where transmissions between students could not be ruled out as a possibility.”

Montgomery County traced 46 cases to suspected transmission in schools, and 30 others to school sports, while Camden County attributed 66 cases to contact in schools. Burlington County reported 24 school-related cases in the last year.

Addressing teachers Thursday, Anthony Fauci, the nation’s top infectious-disease expert, said President Joe Biden’s administration was working to help schools reopen, including by supporting federal funding for masking and better ventilation.

“We’re not going to get back to normal until we get the children back in school,” said Fauci, who wants teachers prioritized for vaccination.

In Pennsylvania and New Jersey most teachers are not currently eligible for vaccination.

Ongoing restrictions

Returning students are likely to notice some changes.

“A number of measures were taken and put in place to prevent a more serious outbreak in schools,” Conaway, the Burlington County health director, said, describing “change in school practices, upgrades to ventilation systems, barriers.”

Among the most important precautions, health experts said, is maintaining distance between students and staff.

“The schools where we’ve seen more linked cases were not distanced properly,” said, Rianna DeLuca, field representative of disease control for Camden County’s health department.

Even as it has encouraged schools to bring students back, the CHOP PolicyLab has not relaxed its guidance recommending six feet of distance in schools. Some schools have reopened more fully by spacing students closer together; in Bucks County, health officials have endorsed a three-foot minimum.

» READ MORE: The wait for a vaccine is frustrating teachers and adding uncertainty to school reopening plans

Some school leaders have resisted reopening more fully to maintain the six-foot guideline.

“Even if we don’t have in-school transmission … we’re still not out of the woods,” said Crisfield, the superintendent in Wissahickon, which isn’t planning full-time in-person instruction for older students. He is concerned about ensuring schools don’t contribute to already high hospitalization numbers and case counts.

With teacher vaccinations delayed, the PolicyLab research group and others have endorsed COVID-19 testing programs in schools. A new program spearheaded by CHOP is providing rapid antigen tests to some area schools, including Philadelphia’s.

Regular testing has two purposes: “easing the concerns” of staff and families, as well as identifying potentially contagious people earlier, PolicyLab’s Rubin said. Had such programs been in place in the fall, he said, it would “answer definitively the question of how many kids were coming in exposed.”

Contact tracing could play an important role, though many people, including students, have been unwilling to share information needed to determine who has been exposed to the virus, Conaway said. That reluctance, though sometimes sparked by a fear of shutdowns, increases the chances that restrictions will ultimately be more drastic.

“We’re seeing a tremendous amount of resistance to the contact tracing process,” he said. “People afraid to rat on friends.”

Even when schools are vigilant, risk can’t be entirely eliminated, said Crisfield, whose Wissahickon district has not seen any cases transmitted in classrooms or sports since reopening full time to elementary students in the fall.

“Sometimes a mask comes down and it’s not supposed to,” he said. “It’s not like we’re perfect, and this is why it’s so tricky.”

In Cheltenham, Marseille, the superintendent, has prepared for Monday’s reopening by “listening to the science” and meeting with health officials. He is trying to balance the desires of community members — a little more than half of whom have opted to send their children back to classrooms. Those who opt out, however, will continue remote learning.

The narrow majority “can’t wait until Monday to put their child on a bus,” Marseille said. But “others are not there yet.”