(CNN) Cars line up before sunrise. Tiny heads stick out of the back seat windows, tightly close their eyes and tilt back as the insides of their noses are swabbed for hints of coronavirus infection.
For children who were exposed to someone with Covid-19 in one of Marietta City Schools' classrooms, early morning testing in a nearby church parking lot has become the routine -- instead of quarantine.
If the exposed students test negative and have no symptoms, they can continue going to school in person -- offering some relief for parents who have been overwhelmed with remote schooling during the pandemic. If the exposed student tests positive, they must isolate at home.
This approach is called test-to-stay, and the US Centers for Disease Control and Prevention is now working with select school districts across the nation to evaluate the practice. Marietta City Schools told CNN that it originally implemented its test-to-stay program on its own; it's now one of the school districts in touch with the CDC as part of its evaluation process.
"In Marietta we have been tracking students who are testing positive through test-to-stay, and it's 3%," Grant Rivera, superintendent of Marietta City Schools in Georgia, told CNN on Monday.
"Three percent of our students who participate in test-to-stay test positive, which means we can keep 97% of them in class," Rivera said. "That is a measure of success."
Under a traditional quarantine program, the 97% of students who tested negative would still stay at home from school.
For its test-to-stay program, any student or staff member who is identified as a school-based close contact of someone with Covid-19 and remains asymptomatic has the option to participate in "test-and-stay."
For example, one week in late September, 318 students and three staff members were eligible for test-to-stay over five days. In that time, 123 tests were performed. Six tests were positive and 117 were negative.
"I think for the foreseeable future, we will be out here every morning on a school day making sure that our kids have this option," Rivera said about test-to-stay.
"We're doing this in Marietta not because we have CDC or public health guidance. Quite candidly, we're doing it because we saw a model in another state," he said. "So, for me as a superintendent who has been tasked to not only develop these solutions but to lead them, I want more guidance from public health based on today's data and today's dynamics."
Federal public health officials have been meeting with states to discuss a potential "test-to-stay" strategy for schools, CDC Director Dr. Rochelle Walensky said last week during a White House virtual coronavirus briefing.
This type of policy would prioritize testing as a way to monitor students who may have been exposed to Covid-19, allowing students to continue to attend classes if they test negative rather than quarantine. But there are still many health experts who agree that quarantines are still necessary.
In an email to CNN, CDC said it views test-to-stay as a "promising practice" and said it's "working with multiple jurisdictions implementing test to stay to evaluate the effectiveness of this strategy." But it's not clear when that test-to-stay guidance could be available.
While there are many different approaches to tracking and containing Covid-19 outbreaks in schools, at least three superintendents -- Rivera; Michael Karner in Lake County, Illinois and Demetrus Liggins in Fayette County, Kentucky -- have all adopted some form of test-to-stay programs in their school districts.
Lake County, Illinois, has been one of the areas sharing data on test-to-stay programs with the CDC. Michael Karner, the regional superintendent of schools and a parent of two children, told CNN that test-to-stay programs have been successful at keeping kids in school safely, if other mitigation measures, such as wearing masks, are in place.
"This program has allowed us to test for in-school exposures -- where in the past last year, if you remember, anybody who was a close contact was quarantined. The big things for us is there must be appropriate, layered mitigation, such as social distancing and mask-wearing," Karner said. "If those are not being followed, then the test-to-stay program would not work for those close contacts."
Data from the test-to-stay program show that for Lake County, fewer than 2% of kids exposed to the coronavirus in classrooms convert to a positive case, Karner said.
"Last year we had lots of students -- hundreds of students -- quarantine just because they were close contacts. But this year, we found that we've been able to keep several hundred individuals that were contacts in schools, and we've also been able to get data with regards to exposure," Karner said.
"Based on all the data that we've gotten in Lake County, we found out that exposure in the classroom is not leading to conversion, which means we're not having many close contacts in the classroom. Most of the close contact situations that we've had with regards to exposure have been on the bus and in the lunchroom," he said. "On the bus, they're very close. Sometimes kids don't wear their masks on the bus. And in the lunchroom, obviously, when students sometimes are sitting closer than the recommended social distancing, that's when we found it."
In Kentucky, Demetrus Liggins said that out of the 402 Covid-19 tests that his school district conducted so far through its test-to-stay pilot program, only four tests yielded positive results.
"We've also found for us that we've had very minimal students that -- since we began this process on September 27 -- have tested positive after returning to school on a normal basis. And there also is an opt-in option," Liggins said "We still have some parents that choose to quarantine their students."
Karner and Liggins both emphasized that their school districts require masking for indoor activities, and that mitigation measure adds to the success of their test-to-stay programs.
In a contrast, Rivera of Marietta City Schools recently announced that for his district, masks now are optional in school buildings and on school buses. The new masking policy went into effect Saturday.
"Marietta recently transitioned to a mask optional approach. The reason for that is several. First of all, we're seeing significant decline in community transmission. We're also seeing a decrease in community positivity rate. Additionally, we're seeing fewer epi-linked cases in our classrooms," Rivera said. "So for us, I don't believe that public health protocol should be static. We have to make sure that our protocols evolve with the data."
The CDC notes on its website that test-to-stay may be a practice comprised of regular testing and contact tracing, but that's also while "maintaining other layered prevention strategies, such as universal masking, to reduce the spread of Covid-19."
As researchers and public health experts continue to examine the data around test-to-stay programs, two studies typically emerge in discussions: one out of Utah and the other out of the United Kingdom.
The study led by researchers at the Utah Department of Health estimates that a test-to-stay program implemented at 13 high schools in Utah collectively saved 109,752 days of in-person instruction for students who otherwise wouldn't have been kept in school.
The study, published by the CDC in May, detailed two state programs in Utah, called test-to-play and test-to-stay.
Under test-to-play, students were tested for Covid-19 every two weeks in order to be allowed to continue extracurricular activities. In test-to-stay, school-wide testing was implemented in response to Covid-19 outbreaks, as opposed to a switch to remote instruction. Researchers credited the test-to-play program with preserving 95% of planned athletic events.
A separate study conducted in England, published last month in the journal The Lancet, found similar rates of symptomatic coronavirus infections among students and staff within schools that follow test-to-stay compared with schools that follow traditional quarantines.
"They found no statistically significant difference between the Covid-19 rates in schools which did implement test-to-stay and those which implemented a more traditional quarantine," said Dr. Meagan Fitzpatrick, an infectious disease transmission modeler and assistant professor of medicine at the University of Maryland, who was not involved in the study.
"This is also supported by modeling work that my group has done, as well as others have done."
Fitzpatrick acknowledged that test-to-stay is a "controversial" approach.
"I think, in my expert opinion, that it should be less controversial than it is," she said. "But I definitely understand why people hesitate and why people are looking for a firmer research basis for the test-to-stay program."
In March, the US Department of Health and Human Services announced it was funneling $10 billion to states to help implement coronavirus surveillance testing in K-12 schools across the country. For most of the test-to-stay programs currently underway, schools have received free Covid-19 tests and some test administrators from their state health departments.
But even with the funding for tests made available in some places, many schools may not have the necessary personnel -- such as school nurses or other staff members -- to organize and coordinate such a large testing operation.
As the CDC continues to evaluate test-to-stay programs, the logistics and resources needed to implement such an approach likely will be a serious part of conversations.
"The number-one difficulty that I have heard, when I discuss these test-to-stay programs here in Maryland, is personnel," Fitzpatrick said.
"When these school districts consider the test-to-stay program, what that requires is it requires somebody to keep track of which students have been designated contacts of the first infection. And so it requires to track who those students are, and to track their test results every day, and to cross-check again that they're getting their tests before they enter the school," Fitzpatrick said.
"Particularly the school nursing staff is already overstretched, and it seems that many of these districts face challenges in getting the additional staff that they would need."