DALLAS, Ga. — The photos showed up on social media just hours into the first day of school: 80 beaming teens in front of Etowah High School near Atlanta, with not a mask on a single face and hardly six inches of distance between them — let alone the recommended six feet.

Amanda Seghetti, a mom in the area, said her parent Facebook group lit up when the pictures of the seniors were posted. Some people thought the images were cute. Others freaked out. Seghetti was in the latter constituency.

“It’s like they think they are immune and are in denial about everything,” Seghetti said.

Pictures of packed school hallways in Georgia and news of positive tests on the first day of classes in Indiana and Mississippi sparked the latest fraught discussions over the risk the coronavirus presents to children — and what’s lost by keeping them home from school. Friday brought reports of more infections among Georgia students, with dozens forced into quarantine in Cherokee County, among other places.

For months, parents and teachers, epidemiologists and politicians have chimed in with their views on the many still-unanswered questions about the extent to which the virus is a threat to children — and the extent to which they can fuel its spread.

A report from leading pediatric health groups found that more than 97,000 U.S. children tested positive for the coronavirus in the last two weeks of July, more than a quarter of the total number of children diagnosed nationwide since March. As of July 30, there were 338,982 cases reported in children since the dawn of the pandemic, according to data from the American Academy of Pediatrics and the Children’s Hospital Association.

President Trump has repeatedly maintained the virus poses little threat to children.

“The fact is they are virtually immune from this problem,” Trump said Wednesday in an interview with Axios.

Eight months after the World Health Organization received the first report of a “pneumonia of unknown cause” in China, much remains uncertain about the coronavirus and children.

Doctors are more confident that most children exposed to the virus are unlikely to have serious illness, a sentiment backed by a report published Friday by the Centers for Disease Control and Prevention that concluded children are far less likely to be hospitalized with covid-19, the illness caused by the virus, than adults. But when children do fall seriously sick, the burden of illness is borne disproportionately: That same CDC report concluded that Hispanic children are approximately eight times more likely and Black children five times more likely to be hospitalized with covid-19 than their White peers.

Early studies on children and the virus were small and conflicting. But accumulating evidence suggests the coronavirus may affect younger children differently than older ones.

For example, doctors say the multisystem inflammatory syndrome linked to the virus known as MIS-C — that has appeared in a small number of children weeks after infection presents differently in younger children than in teens and young adults. Infants and preschoolers who have been diagnosed with the syndrome have symptoms mirroring Kawasaki, a disease of unknown cause that inflames blood vessels. In the older group, the consequences appear more severe, with doctors describing it more like a shock syndrome that has led to heart failure and even death.

Several studies suggest adolescence could mark a turning point for how the virus affects youths — and their ability to spread the pathogen.

One paper published in July in the journal JAMA Pediatrics found that children younger than 5 with mild to moderate cases of covid-19 had much higher levels of virus in their noses than older children and adults — suggesting they could be more infectious. That study, conducted by doctors at the Ann & Robert H. Lurie Children’s Hospital of Chicago, used data from 145 children tested at drive-through sites in that region.

A study out of South Korea examining household transmission also found age-based differences in children. Puzzlingly, it seemed to reach an opposite conclusion about transmission than the Chicago researchers did. Children under age 10 did not appear to pass on the virus readily, while those between 10 and 19 appeared to transmit the virus almost as much as adults did.

Max Lau, an epidemiologist at Emory University tracking superspreader events in the state in collaboration with the Georgia Department of Public Health, said two striking trends have emerged even as work continues on an analysis of recent data.

Disease detectives have found relatively few infections among young children even after the state loosened its coronavirus-related shutdown. Researchers elsewhere have noted there hasn’t been a clear, documented case of a young child triggering an outbreak. In contrast, cases spiked among 15- to 25-year-olds, suggesting they may be driving the spread of the virus.

“When the shelter-in-place lifted, they perceived that they could go back to normal life and that’s what I observed,” Lau said.

In May, Jerusalem’s Gymnasia Ha’ivrit high school was the center of a major outbreak that public health officials said seeded transmission to other neighborhoods. In June, an overnight YMCA camp in Georgia was forced to close after 260 of 597 children and staff members tested positive for the virus — an event some experts heralded as a parable for what can happen when young people are allowed to gather without being attentive to wearing masks or maintaining physical distance. At that camp, the first to come down with symptoms and be sent home was a teenage counselor.

Other gatherings among teens have led to smaller outbreaks. In New Jersey, it was a party at a country club that left at least 20 teens infected. In Michigan, health officials said more than 100 teens in three counties have tested positive since mid-July following graduations and other parties.

Sadiya S. Khan, an assistant professor of cardiology and preventive medicine at Northwestern University’s Feinberg School of Medicine, said social practices, rather than biology, may explain why teens and young adults appear to be spreading infection.

“They are more likely to be out and about. They are more likely to not have experienced any consequences,” Khan said. “There has been a lot of attention to the fact that people who are older have a worse course and if you’re young, it doesn’t feel as dangerous, so they might think, ‘Why be as careful?’ ”

Khan said she worries schools that don’t enforce mask-wearing and social distancing can be laboratories for superspreader events rippling out to the broader community.

Medical history tells us that children’s role in infectious diseases is not always what we first assume. In 1960, in response to significant deaths among the elderly during the 1957-1958 influenza pandemic, the surgeon general recommended flu vaccines for people 65 and older. It wasn’t until decades later that studies showed that mortality among older people could be reduced by vaccinating the young. In 2002, the CDC recommended flu shots for infants and in 2008 expanded that to school-age children.

With the coronavirus pandemic, like any disease outbreak, research takes time, and experts say decisions being made about reopening schools are necessarily being made without the full picture of the risk the virus poses to children.

For example, the CDC’s study of that Georgia YMCA camp did not include detailed tracing of how cases spread among campgoers. Did one teenage counselor spread the virus to the whole camp? Did that counselor infect a few younger children, who in turn infected other younger children?

Similarly, that study did not document what happened to families of the infected when the children returned home. Did they bring the virus back to their families, thereby dispelling the notion that children do not transmit the virus to adults? Or, if infections did spread, was it simply the result of high viral prevalence in Georgia, and not the result of contact with a campgoer?

As the case of the Georgia camp illustrates, measuring the risk younger children face in returning to school continues to be an inexact art. Parents are left with the agonizing and anxiety-riddled task of evaluating that potential peril for themselves. And they must weigh the potential health risks of the virus against the educational, social, developmental and economic consequences of children remaining out of the classroom.

Teachers unions from Florida to Ohio have protested plans to fully reopen schools, arguing that even if a few months of data suggests children are not likely to suffer severe outcomes from the virus, they could still pass it to vulnerable adults.

On Aug. 2 — hours before the first day of school — the principal of North Paulding High School near Atlanta sent a letter to parents informing them of coronavirus infections on the football team. Video on the Facebook page for the team’s parent-run booster club showed members of the team, with no masks or distance between them, lifting in a weight room as part of a fundraising event a week earlier.

On the first day of school, students posted a picture of hallways crammed with unmasked classmates. One student was initially suspended for posting the pictures. The school overturned that suspension Friday.

Within days, the school burst into the national spotlight, and the issue spawned heated arguments in a local Facebook group called “What’s Happening Paulding,” with parents occasionally descending into name-calling and expletive-laced tirades as they argued over whether the pictures should warrant concern. Sunday night, North Paulding High sent a letter to parents announcing the school would be closed to in-person learning for at least two days because of nine cases of the coronavirus.

John Cochran, the father of a ninth-grader and middle-schooler in the Georgia school system, said in an interview he felt it wasn’t safe for his children to attend school in person, in part because multiple adults in their family are immunocompromised.

“That was one thing we stressed to the kids — they’ve got too many adults that they are regularly in contact with who could be in bad shape if they pick this up from them,” Cochran said. “Personally, I didn’t want that on my kids’ conscience that they went to school and got their mother, stepdad, dad or grandparents sick.”

In Georgia’s Cherokee County, where the 80 students gathered for that unmasked photo, Seghetti said she knows she’s in the minority in deciding to keep her 11-year-old son, Kaiden, home from school.

Seghetti said after seeing photos shared by parents from inside schools and learning that two elementary campuses in the district already had reported coronavirus cases — a second-grader Tuesday and a first-grader Wednesday — she is confident she made the right decision. Cherokee County schools spokeswoman Barbara P. Jacoby said the schools have implemented changes to try to keep students safe, including staggering bell times to avoid hall crowding and providing students with two masks each they can wear if they wish.

Karin Jessop’s two children, ages 12 and 13, attended that YMCA day camp at Lake Burton where the residential camp outbreak unfolded. Her children, who were at the camp for four weeks but came home each night, did not get infected; the outbreak was among those who stayed overnight, another reminder of the unpredictability of the spread.

Jessop, a technology company executive, said after news of the outbreak broke, “a lot of moms were getting stressed out about making the wrong decision and worried what people will think.”

“At the end of the day, it’s your family,” she said, adding she believes staying home affects her children’s development, which makes the camp experience worth the risk.

“Many of these kids have been home since March, and if you have super gregarious, extroverted kids, they are used to and need that interaction.”

Janes and Cha reported from Washington.