As COVID-19 cases surge — leaving a number of local schools without adequate staffing to operate in person — administrators should take steps to keep more teachers and children in classrooms, according to Children’s Hospital of Philadelphia and its PolicyLab research group.

At the same time, the Philadelphia Department of Public Health has adjusted its recommendations around the COVID-19 positive threshold at which city schools should temporarily close. Now, 10% of a school’s staff and students must test positive for a school to close, up from 3%.

The CHOP recommendations — which still include universal masking in schools but drop asymptomatic testing for staff and students, and lower quarantine lengths — reflect a shifting analysis that prioritizes in-person education over the risks of what the research group described as a largely milder omicron variant.

Guidance released by PolicyLab on Wednesday and endorsed by the hospital’s leadership advises that students or staff who test positive for the virus be allowed to return to school five days after symptoms began, if their symptoms disappear or are resolving, rather than the prior 10-day quarantine recommendation.

And those who are close contacts of someone with COVID-19 not in their household should be allowed to stay in school as long as they are asymptomatic and masked for seven days — what PolicyLab is calling “mask to stay.”

“With evidence that COVID-19 is becoming a milder infection in most children, and at a time when all adults and youth in K-12 settings have been offered vaccination, our PolicyLab experts and CHOP clinical leadership have reached a consensus that preserving as much in-person schooling as possible outweighs the risks of infection to children and school staff at this stage of the pandemic,” the group said in a statement.

David Rubin, PolicyLab’s executive director, said in an interview that many public health recommendations “are no longer feasible or practical for most schools.”

“We need to recalibrate and start to think about COVID in the context of how we think about other seasonal viruses,” he said.

Both Philadelphia and suburban schools have relied heavily on CHOP and city guidance in the past, but it was not immediately clear when changes might be adopted at local schools.

Upper Darby Superintendent Dan McGarry said Thursday his Delaware County school system would move to adopt CHOP’s guidelines beginning Monday. The district will stop asymptomatic testing and limit contact tracing — and is keeping mandatory masking.

“Our nurses were just totally overwhelmed prior to the break. It’s become nearly impossible to contact trace appropriately with this amount of spread,” said McGarry. “The real focus is now, ‘If you’re sick, stay home and isolate for those five days, and then you can get back to work and get back to school.’”

Philadelphia School District officials did not respond to a request for comment.

“With guidance and support from the Philadelphia Department of Public Health and Children’s Hospital of Philadelphia, we can continue to keep our school doors open safely,” Superintendent William R. Hite Jr. said in a motivational email sent to staff Thursday, “but it will take all of us doing everything we can to keep ourselves healthy and continuing to show up everyday.”

Philadelphia Department of Public Health spokesperson James Garrow said the old 3% positive school-closing threshold for city schools was written when COVID-19 cases were “comparatively rare, and our guiding principle was to identify outbreaks before they really got started so we could pause the school and interrupt transmission. Today, with cases seemingly everywhere, it’s not difficult to find that 3% of just about any public population has tested positive.”

Because the department believes in the value of in-person learning, Garrow said, it moved this week to adopt the Council for State and Territorial Epidemiologists’ definition of a school cluster, which is 10%.

“We believe that if 10% of a school population has tested positive, that is a level of risk that is greater than pausing in-person education. Our trigger point for pausing in-person education was much more conservative than others, but now we’re in line with what national experts recommend,” said Garrow.

Separately, the CHOP recommendations advise schools to no longer require testing of asymptomatic staff or students, though they could offer voluntary testing if resources allow for people with personal or family health issues.

It also isn’t essential for students or teachers with mild symptoms to be tested, according to the recommendations. Instead, they should assume they have COVID-19 and isolate at home for five days, then return if symptoms are improving.

Some districts — including Philadelphia — now test all staff weekly.

Rubin said the aim was to reduce the burden on school staff to implement testing programs — describing universal masking as a more viable option to curb spread while the virus is surging.

“We have to become comfortable that we don’t need to know about every individual who might be asymptomatic, recognizing that people are still wearing masks at periods of high transmission,” he said. “And we have to be comfortable that we cannot entirely eliminate risk from our school environments.”

Masking policies vary in Pennsylvania school districts since the state Supreme Court struck down the mandate from Gov. Tom Wolf’s administration. Many in the Philadelphia region — including the city’s schools — still require masking, though a number of districts, including in Bucks County, have gone mask-optional. Children and staff in New Jersey schools must still mask.

Rubin said that districts considering dropping masking requirements should wait until cases and hospitalizations are declining, “so that you can at least help our community hospitals.”

But as to whether keeping schools open would contribute to the strain on the health-care system, Rubin said that much of the transmission that has driven the current spike in cases stemmed from holiday gatherings.

“I would argue that schools are no longer meaningfully contributing to the challenges that the adult health systems are having,” he said. “The answer is that people need to get vaccinated, and if eligible, receive their booster.” He added that essential workers rely on schools and daycares, and shutting those contributes to shortages in the health-care system.

The recommendations drew immediate alarm from the Philadelphia Federation of Teachers.

PFT president Jerry Jordan said the union wants schools to be open for in-person learning, but said he was “deeply concerned” about both the CHOP and city health department recommendations.

“Quite frankly, the recommendation to effectively end asymptomatic testing feels like a very ill-advised effort to downplay COVID cases and sweep our concerns regarding a massive surge under the rug,” Jordan said in a statement.

The threshold changes, he said, were an “arbitrary shift that again feels like a way to simply keep school buildings open no matter the cost to students and staff.”

The Philadelphia Public Health Department has continued to call for 10 days of isolation for students or staff who test positive for COVID-19. Health Commissioner Cheryl Bettigole said Wednesday that the department’s latest guidance was issued before the CDC clarified that the five-day recommendation applied to schools.

She said the department is now discussing the issue internally and weighing the shortage in tests and the high number of cases against the benefits of in-person learning.

“My guess is that those conversations will take another few days,” she said.

Rubin said PolicyLab went further than the CDC in endorsing a “mask to stay” approach for students and staff who are close contacts of people with COVID-19 not in their households. He cited school testing programs that he said found 2% to 3% of children identified as close contacts went on to test positive.

And for staff who don’t have symptoms, “it was another way to get more staff back and try to help schools manage through the worst of this,” he said.

Staff writer Laura McCrystal contributed to this article.