The trends for older children are much harder to discern. But over all, they suggest a greater chance for infections to spread without careful measures in place.
Sweden, often cited as a model for having schools operate throughout the pandemic, kept schools open for children under 16, but with small class sizes and physical distancing. According to one recent study, opening elementary schools had limited impact on parents, but teachers in schools with older children had double the rate of infections compared with those who taught remotely.
In Israel, crowded high school classrooms seeded outbreaks, prompting the health ministry to release a report this week calling children superspreaders. And in the United States, some high school reopenings have been disastrous, like those of a Georgia school shamed for unmasked students in its hallways and a high school in Utah where infections flared to 90 cases within two weeks.
A significant proportion of cases seem to come from activities outside school, Dr. Rubin said. “Most of the transmission, when we see it, is occurring in carpools, during travel leagues, maybe in a locker room, or parties and gatherings that people have on the weekend,” he said.
“You’ve assumed that by closing schools, that’s going to negate the problem,” but informal settings that are less regulated may sow more infections, Dr. Rubin said.
The data from Britain suggests, however, that clusters even among older children may not always lead to infections at home. Random testing in schools there showed sharp increases in infections among children older than 11, but the spikes did not seem to translate to a rise in adult cases.
“I find this fascinating and something that we need to understand more,” Dr. Nichols said.
Despite the gathering research, Boston on Wednesday decided to close schools even as restaurants, casinos and gyms remain open. Dr. Jenkins, who has two children, said she was particularly frustrated by the news.