A child receives a dose of the Pfizer-BioNTech coronavirus vaccine at an elementary school vaccination site in Miami. (Eva Marie Uzcategui/Bloomberg News)

Students who have been exposed to the coronavirus can safely continue in-person learning if they are regularly tested for the virus at school, avoiding disruptive at-home quarantines, the Centers for Disease Control and Prevention said Friday.

The CDC released two studies that show the effectiveness of what’s known as “test-to-stay.” School districts across the country have tried this strategy, though it is not widely used.

“These studies demonstrate that test-to-stay works to keep unvaccinated children in school safely,” CDC Director Rochelle Walensky told reporters Friday. She called it “a promising and now proven practice.”

Typically, students who are deemed close contacts of someone who tests positive for the virus are sent home to quarantine, to make sure that people who may be carrying the virus, even without symptoms, do not infect others. The CDC studied test-to-stay alternative programs in Lake County, Ill., and Los Angeles County.

“Test-to-stay is an encouraging public health practice to help keep our children in school," Walensky said.

Children ages 5 to 11 became eligible for the two-dose coronavirus vaccine from Pfizer on Nov. 2, 2021. (Video: Luis Velarde/The Washington Post, Photo: Cincinnati Children’s/The Washington Post)

Quarantines of students have been controversial because they interrupt learning as schools are laboring to make up for months of often substandard remote education. They also force many parents to scramble for child care at the last minute. With positive cases rising, the number of children in quarantine has also been climbing quickly.

Education Secretary Miguel Cardona welcomed the news, particularly in light of evidence of the harm caused by remote schooling. “Schools across the country must do everything possible to keep students safe and ensure that they are able to access high-quality, in-person instruction safely in their schools,” he said Friday.

But test-to-stay requires significant resources. There is a shortage of the rapid tests used by schools. And these programs require school personnel to administer the tests, something not every school district is able to muster. Twelve states have created policies that allow test-to-stay programs, the CDC said: Illinois, Maine, Massachusetts, Michigan, Missouri, New Mexico, Oregon, Pennsylvania, Rhode Island, Utah, Vermont and Washington state. Districts in other states may still have programs created on their own.

Rapid coronavirus tests are still hard to find in many places, despite Biden vows

Walensky said CDC would update its materials to help schools and parents implement this approach. However, in the face of rising case counts and concerns that all districts cannot mount a test-to-stay program, the agency opted against updating its formal guidance to schools to recommend a switch to test-to-stay.

That guidance still recommends that unvaccinated students who come into close contact with a person who has the virus should quarantine for seven to 14 days after exposure.

The two new studies, published in the CDC’s Morbidity and Mortality Weekly Report, looked at how test-to-stay was implemented this fall.

In both cases, Walensky noted, students wore masks. Close contacts of the people who tested positive were monitored for symptoms and told to stay home if they became sick. Contacts who came back to school were regularly tested — at least twice over the seven days after exposure.

In Los Angeles County, about half of the 78 school districts, which include 21 percent of the county’s schools, used test-to-stay instead of quarantine this fall. In those schools, there were 20 outbreaks identified but transmission was no higher than before the program was adopted.

Students in county schools using quarantine, including the largest district, Los Angeles Unified, lost a total of more than 92,000 in-person school days, where students in test-to-stay programs lost none.

The test-to-stay program is just now being rolled out in Oregon but is already popular with districts, said Jim Green, executive director of the Oregon School Boards Association.

“We’ve had to quarantine kids for up to 14 days,” he said. “Given everything that’s gone on in the pandemic is that what’s best for kids? Do you want kids out of school just because they’ve come in contact with someone with covid? If we can do a rapid test and show they are negative and keep them in school, that’s our goal."

The pandemic’s impact on education

The latest: Updated coronavirus booster shots are now available for children as young as 5. To date, more than 10.5 million children have lost one or both parents or caregivers during the coronavirus pandemic.

In the classroom: Amid a teacher shortage, states desperate to fill teaching jobs have relaxed job requirements as staffing crises rise in many schools. American students’ test scores have even plummeted to levels unseen for decades. One D.C. school is using COVID relief funds to target students on the verge of failure.

Higher education: College and university enrollment is nowhere near pandemic level, experts worry. ACT and SAT testing have rebounded modestly since the massive disruptions early in the coronavirus pandemic, and many colleges are also easing mask rules.

DMV news: Most of Prince George’s students are scoring below grade level on district tests. D.C. Public School’s new reading curriculum is designed to help improve literacy among the city’s youngest readers.