The New York Times reports that scientists are converging on a consensus that it is safe for young children to return to school.

After a summer of uncertainty and fear about how schools across the globe would operate in a pandemic, a consensus has emerged in recent months that is becoming policy in more and more districts: In-person teaching with young children is safer than with older ones, and particularly crucial for their development.

On Sunday, New York City, home to the country’s largest school system, became the most high-profile example of that trend, when Mayor Bill de Blasio announced that only elementary schools and some schools for children with complex disabilities would reopen after all city classrooms were briefly shuttered in November. There is no plan yet to bring middle and high school students back into city school buildings.

It was an abrupt about-face for the mayor, who had for months promised to welcome all of the city’s 1.1 million children — from 3-year-olds to high school seniors — back into classrooms this fall.

But the decision put New York in line with other cities around America and across the world, which have reopened classrooms first, and often exclusively, for young children, and in some cases kept them open even as they have confronted second waves of the virus.

In-person learning is particularly crucial for young children, who often need intensive parental supervision to even log on for the day, education experts say. And mounting evidence has shown that elementary school students in particular can be safe as long as districts adopt strict safety measures, though it’s an unsettled question for older students.

“With younger kids, we see this pleasant confluence of two facts: science tells us that younger children are less likely to contract, and seemingly less likely to transmit, the virus,” said Elliot Haspel, the author of Crawling Behind: America’s Child Care Crisis and How to Fix It. “And younger children are the ones that most need in-person schooling, and in-person interactions.”

Districts including Chicago, Washington D.C. and Philadelphia have either begun to bring back only young children or have plans to do so whenever they eventually reopen classrooms.

In Rhode Island, Gov. Gina Raimondo, a strong proponent of keeping schools open, recently asked colleges to shift to all-remote learning after Thanksgiving, and gave districts the option of reducing the number of high school students attending in person. But she asserted that middle and elementary schools were not sources of community spread.

That model of giving priority to younger students has been pioneered in Europe, where many countries have kept primary schools open even as most other parts of public life have shuttered during the continent’s second wave.

Italy has kept its primary schools open but kept teaching remote for middle and high schools. All schools in Germany are open, and discussions about possible closures have focused mainly on high schools.

And in America, more and more districts have begun to prioritize elementary school students for in-person learning.

In urban districts that have been slow to reopen, that has meant making plans to bring back the youngest students. In parts of the Midwest where school districts were more aggressive about reopening, and where there has been a huge rise in cases in recent weeks, public health officials have prioritized keeping elementary schools open even as they have closed high schools and in some cases middle schools.

“The data is becoming more compelling that there is very limited transmission in day care and grade schools,” said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota and a member of President-elect Joseph R. Biden Jr.’s coronavirus task force, in a recent interview.

“I keep telling people, ‘Stop talking about kids — talk about those younger than 10,’” he added. “We’re seeing a very different epidemiology in that group than we’re seeing, for example, in high school students.”