Every two weeks of the spring 2021 semester, Denise Watson pulled up to Michelle Upperman’s first-grade class at Southern Elementary School in New Castle, Delaware. Watson came bearing nose swabs and antigen test kits from the local healthcare clinic where she worked.

By the end of May, the students expected her. And many among them were used to her technique: They’d been swabbed every two weeks that spring as part of a district-wide program. She brought the kids into the hallway one at a time, sampling each small nose. “They come up and they just tell the kid, ‘I’m gonna do a little tickle-tickle in your nose!’ … The kids don’t even know that it’s happening,” Upperman says, praising Watson and her team.

After the swab, the students got stickers—often making their classmates who weren’t enrolled in the program jealous. Watson ran the tests using Abbott’s BinaxNOW cards, small pieces of cardboard with embedded chemicals that can detect coronavirus proteins on the outside of the virus. (Slower PCR tests multiply the genetic material in a sample to look for the coronavirus.) Within fifteen minutes, a test card displayed a single colored line for negative, or two lines for positive. Double stripes triggered a PCR test to confirm the result, followed by isolation, contact tracing, and other safety measures at the school—all well-practiced by staffers ranging from school nurses to district-level administrators.

Southern Elementary, part of Colonial School District, is one of almost a hundred schools across Delaware relying on antigen tests as part of its safe reopening strategy, which the state plans to expand this fall.

The tests enabled many schools to regularly screen their students for the coronavirus without racking up huge expenses; BinaxNOW tests cost just $5 each, while PCR tests may run upwards of $100 a pop. This type of regimen—called “surveillance testing” by public health experts—has caught cases, here and elsewhere, before they could turn into outbreaks and provided a sense of security for the families who chose in-person learning. 

Based on those successes, school districts in other states are now considering similar programs with cheap, fast options that may make classrooms safer in the fall, as the Delta variant compounds reopening challenges. Despite its promise, however, a lack of data on these efforts makes it difficult to evaluate just how effective regular testing may be at preventing COVID-19 outbreaks in classrooms.

binaxnow rapid covid antigen test
The BinaxNow test comes as a small card that shows results in just 15 minutes. Abbott

Delaware public health officials became interested in using rapid tests fairly early in the pandemic, says Rick Pescatore, Chief Physician for the Delaware Division of Public Health. He saw the potential for disease monitoring in schools and other settings.

Once antigen tests began receiving Emergency Use Authorization from the FDA in the summer of 2020, Pescatore and colleagues started a pilot program at the Salesianum Catholic school in Wilmington. Other districts and individual schools soon followed. “Once one school district saw the success of another, they quickly jumped onboard,” Pescatore says, referring to the ease of spinning up such programs.

The Colonial district had an advantage compared with other schools: an existing partnership with a community clinic. Life Health Center, based in nearby Wilmington, runs five school-based wellness hubs that were integrated with the district before COVID-19 hit. The connection provided Colonial with expertise and staff who could perform the screenings (including Denise Watson), while the state provided the antigen test supplies. “We were in such a good position to get started because we already had been working for the last five years with Life Health Center,” says Jon Cooper, Division of Behavioral Health at Colonial and the district’s lead COVID-19 coordinator.

Initially, some Delaware parents may have been surprised to hear their schools were relying on antigen tests as part of their reopening strategies. While the kits are much more convenient than PCR ones—they’re cheaper, faster, and can be administered at a school without the need to send samples off to a lab—the convenience comes at a cost. They have a lower sensitivity rate, meaning that they’re more likely to provide false negatives. (Sensitivity rates vary by manufacturer, but may be as low as 70 percent, while PCR tests have sensitivity rates much closer to 100 percent.) In other words, students who receive a negative result may still be infected with the coronavirus, and capable of spreading it to their classmates and teachers.

For a school setting, however, Pescatore says the convenience outweighs accuracy concerns. Children are likely to experience mild coronavirus symptoms or none at all, but they tend to be most capable of spreading the disease soon after they’re infected; that’s why a rapid test is an invaluable way of identifying—and isolating—potential cases before they turn into outbreaks. This quick identification is thus incredibly valuable, even if the efforts don’t catch every single asymptomatic case.

Similar programs outside of Delaware also prioritize quickness and convenience. In Baltimore, Maryland, for example, the biotech company Ginkgo Bioworks partnered with the city to provide tests that students are able to administer themselves. The company uses a method called pooling, which checks samples from an entire classroom at once, allowing for quick results (within 24 hours), while still using PCR and other highly accurate tests that look for the virus’s genetic material. Other pilot programs have relied on this technique or rapid tests, depending on what is most convenient for a district and its partners.

At the Colonial schools, Watson and her Life Health Center teammates backed up any probable cases with a more precise, rapid PCR test, following CDC guidance. After months of use, Watson doesn’t have accuracy concerns: “When we’ve run a positive antigen, the positive PCR comes right behind it.”

The surveillance program caught many asymptomatic cases. One child from the district’s pre-K program tested positive without any fever, cough, or other tell-tale signs. Their parent tested positive, as well, Watson says. “That was really helpful to her and her family.” (Life Health Center offered testing to all family members connected to a positive case.)

Colonial’s system particularly shone after the district’s spring break in early April. While the Life Health Center staff had been testing enrolled students every two weeks, they decided to swab all 700 of those in the program in one week right after spring break. That round of testing identified a few positive cases that may not have been caught in the normal rotation. During the off days, Watson says, children are “in different households, exposed to what they aren’t typically exposed to.” 

Despite worries that school buildings may be superspreading COVID-19 hubs, Delaware’s contact tracing program has found cases tend to come into schools from family gatherings, extracurriculars, and other community activities—not the other way around.

MOT Charter School, a K-8 school in Middletown, Delaware, also used antigen tests to prevent coronavirus spread after vacations. Administrators set up a drive-through site prior to students’ return from winter break. “They were able to identify those positive cases so that [the students] didn’t show up for school that first day back after a long holiday break,” says Ann Covey, a school nurse specialist at the Delaware Department of Education.

We were getting consent forms for kids to be tested on the last testing day for their school.

Denise Watson

Swabbing students every two weeks is just one part of surveillance testing. The Delaware public health agency required schools to report every single result. Watson described this as a “bit labor intensive:” the Life Health Center team needed to manually type in the name, address, and telephone number of every student tested, along with the result and answers to symptom screening questions.

Manual reporting processes like this one are common among local public health departments that did not have the computing hardware necessary to automatically upload results to state and federal agencies. In many states, the challenges of reporting antigen tests have allowed these numbers to entirely slip through the cracks. PCR tests, by comparison, are typically evaluated by large laboratories or hospitals with established electronic data portals.

As a result, antigen results are chronically underreported, as described by the COVID Tracking Project, Kaiser Health News, and others. In March 2021, the US was conducting four million antigen and other rapid tests daily, according to an HHS report—that’s double the number of PCR tests at that time. Yet for the majority of those swabs, there are no public data on where they happened, who was tested, or what the results were.

This is even true in Delaware, where every antigen test conducted in a public school is carefully tracked. When asked if he could provide statewide testing data to Popular Science, Pescatore said, “not within six months.”

The lack of data makes it difficult to evaluate just how effective school testing programs are at protecting students and staff. Still, limited information from the schools that do track their results suggests that the swabs are helping keep school transmission in check by weeding out cases. In New York City, where students must opt into mandatory testing in order to attend class in person, the school district’s test positivity rate has consistently been well below one percent. That’s in line with what Delaware saw. About one-third of schools had programs in place by the end of the spring semester, and Pescatore says the positivity rate was “far below one percent.”

Facing limited capacity for data tracking, avoiding outbreaks is a win for Delaware, but other  efforts may have different ambitions. “The big question [for data reporting] is, what is the overall goal of the testing program?” says Dan Larremore, a statistician at the University of Colorado whose recent work has focused on antigen tests. Other efforts may, for example, want to catch every single case or understand more granularly who is spreading the coronavirus to whom. 

The process for the Colonial School District and other Delaware schools aimed to curb hotspots without shutting down entire classrooms. That meant their priority was communicating results to staff, students, and their families. A duo of positive antigen and PCR tests would trigger a round of contact tracing, followed by individual notifications to any students and staff who may need to quarantine. “Our process really has been to look at each case on an individual basis, so that we’re not putting out more individuals than we have to,” says Cheri Woodall, Behavioral Health Coordinator at the district. 

Public notifications were an important part of the strategy as well. After all close contacts had been notified, the district would release a statement (online and directly to families) that included the building where a case was identified and the last day that individual was in the building. Administrators aimed to get up those notices by 6 p.m. the day a case was found. “We want to be as maximally transparent about this as possible,” says Cooper.

graph showing rising number of antigen testing done on teachers and students throughout the year
Note that the school year ended in June. Infographic by Sara Chodosh

The majority of in-person students did not opt into Colonial’s testing program. Out of about 4,000 students enrolled in face-to-face instruction at the end of the spring semester, only 700 participated in testing—a rate of about 18 percent. The enrollment rate was higher in the district’s eight elementary schools (26 percent) compared to the middle and high schools (seven percent). There is little or no public data about how other similar programs fared across the US.

By all accounts, the district was communicating well with teachers and families, making the tests convenient, and providing everything free of charge. Leslie Cansler, the parent of a special-needs child in the school system, says she “felt safe” sending her son back and found the district to be very transparent.

So why the low enrollment numbers? Cansler suggested some parents may be concerned about privacy, not wanting a school system to collect medical information about their children. Some parents also may have found the tests unnecessary, believing in well-publicized—yet highly critiqued—evidence showing that children may be less likely to spread the coronavirus compared to adults.

A district can always put in more effort to address questions and concerns, says Andrew Sweet, managing director for pandemic response programs at the Rockefeller Foundation, who has worked with the state and other school testing pilot programs. Larremore, the statistician, echoes that sentiment, saying that every parent will have unique motivations behind the health choices they make for their child.

Data do suggest that testing can help parents feel safer sending their children to school in person. In a June RAND survey commissioned by the Rockefeller Foundation, 75 percent of parents unsure about fall 2021 in-person said that regular COVID-19 testing would help. But there’s a difference between a theoretical program described in a survey and an actual one implemented by a school. 

Testing programs are “most successful in communities where you have an education leader saying, ‘this is why it’s important, this is a tool that will enable your child to continue learning,’” Sweet says. At the Colonial schools, questions and concerns about the effort were redirected to already overworked school nurses.

Colonial’s low enrollment also speaks to the time that it takes for a school district to build trust in a new public health program. Though the district began testing in March, families continued turning in consent forms through the end of May. “We were getting consent forms for kids to be tested on the last testing day for their school,” Watson says.

Whether this continued enrollment was driven by parents realizing the program’s value, kids who wanted five minutes in the hallway and a special sticker, or some of both, it suggests that Colonial may be screening more students in the fall.

Delaware’s program will be ramping up in the fall, even as more teachers and students get vaccinated. The state had a head start on other state agencies now deciding how to use funding from the American Rescue Plan specifically devoted to school testing, Sweet says. Some districts are planning to use antigen swabs, while others will utilize different fast and convenient options from the growing COVID-19 screening landscape.

Colonial plans to continue checking those who are vaccinated. Karen Kleinschmidt, lead nurse and COVID-19 coordinator at nearby Christina School District, has similar plans. She’s carefully watching the rise of variants—especially the Delta variant now causing the majority of cases in the US—and has seen breakthrough cases in her district. Delta is much more transmissible than past COVID-19 strains; while vaccines work well against it, children too young for inoculation are more vulnerable. 

School surveillance testing may be particularly useful in communities where vaccination rates are low, Larremore says, as variants are more likely to spread through those populations.

As they continue testing, Pescatore says Delaware public schools are considering how similar testing technologies and school-health partnerships may help prevent future disease outbreaks. “It is a remarkably exciting horizon when it comes to public health and education combining forces.”