The rush by countries to shut down schools was one of the first instinctive global responses as covid-19 began scything through populations. Now, as some nations cautiously ease lockdowns, there is far less consensus on how and when to reopen classes.

A big question is what type of setting will work with kids being kids: mingling, playing and trading lunches.

But wider issues on how schools fit into the infection curve are also getting a closer look.

A study published April 6 in the Lancet — and a separate paper by the Organization for Economic Cooperation and Development — suggest that school closures are less important than workplace closures in stemming the spread of the novel coronavirus, which causes the disease covid-19.

Still, few reopening decisions are more sensitive than when to send students back to class. The huge range of policies around the world — some schools shut for the academic year and others moving to reopen — offer a preview into the contrasting speeds and priorities for the eventual rebound from life under the pandemic.

Denmark is a case in point.

It reopened lower-level schools Wednesday, but some parents argued that it was too soon and vowed to keep their children home. France, Germany and Australia are among countries making plans to reopen schools, some as soon as this month.

At the same time, educators and others worry about possible setbacks for children caused by extended schools closures, particularly for those who lack access to online schooling.

‘Endlessly balancing risks’

It all points to the central conundrum of this pandemic era: how to move away from the lockdowns without triggering a devastating second wave of infections.

“Anything we do when we exit lockdown is not without risk. But once we pass the peak, the balance of risks takes us to definitely gradually starting to reopen schools early in the exit from lockdown,” said Russell Viner, an author of the Lancet study and president of the Royal College of Pediatrics and Child Health in London.

He says the data suggests that children have not been super-spreaders of the coronavirus. But schools, he said, should introduce social distancing, ensuring that students do not mix during breaks, and should provide protective gear for teachers.

But some places are not yet ready. Italy, Spain and Austria will put shops, manufacturing and construction back to work before reopening schools. In Wuhan, China, the source of the outbreak, the lockdown was eased April 8, allowing 11 million people to get back to work — but not school.

Across the United States, school closures are a patchwork of policies. Some states, including Maryland, are considering opening before the end of the academic year. Other places, including Virginia and the District, have shut down schools through the summer.

“We’re endlessly balancing risks,” Viner said.

School decisions vary widely

There are a few outliers: countries that did not close schools or even extend school holidays.

Tajikistan, an authoritarian former Soviet state in Central Asia, claims that there are no covid-19 cases within its borders and that schools are in session.

Nicaragua has bucked the trend in Central America, where some countries have taken aggressive measures against the coronavirus with curfews, quarantines and border closures. Nicaragua’s public schools remain open and the government hasn’t imposed restrictions on private- or public-sector employees. Pro-government marches and religious processions have continued.

Turkmenistan and Belarus also have generally rejected emergency health measures and have largely kept schools open — but extended holidays by a couple of weeks.

Other nations acknowledged the crisis but prioritized schools.

In Taiwan, deemed a success story in its handling of the coronavirus, students have been back at school since late February, after holidays were extended because of the virus. Sweden has kept schools open for children under 16, along with cafes, bars, restaurants and some other services.

But views on schools reopening vary wildly, even among neighbors and within countries.

Australia’s government, having flattened the curve to less than 1 percent growth in daily cases, said medical advice has been consistent: The risks of keeping schools open are “very low,” and schools remain the best place for children to learn. Yet some Australian states ignored this. Only about 5 percent of pupils, mainly children of essential services workers, are still in schools in some places.

“Our children’s education hangs in the balance,” Australian Prime Minister Scott Morrison said Wednesday in a televised statement that was criticized by teachers union officials.

Morrison said that swiftly reopening schools is crucial for “those students who we know won’t get an education at home. It’s a sad reality but we know it’s true and we need to face it.”

Australian Education Minister Dan Tehan said his 16-year-old daughter was returning to school and called for schools across Australia to resume face-to-face classes within a month. New South Wales, Australia’s largest state, plans to stagger pupils’ return to school starting April 28.

What studies have found

School closures are intensely stressful for many parents, who are fearful their children may fall behind. High school seniors worry about how they may be graded and the impact on university admission. Studies also suggest that extended school closures have a lasting impact.

According to UNESCO, 91 percent of students — more than 1.5 billion children — are impacted by school closures, with nationwide closures in 191 countries. The U.N. agency warned that dropout rates are likely to climb after schools reopen. The longer the closures, the deeper the impact.

The Lancet study, led by University College London, found that school closures could have a relatively small impact on the coronavirus’s spread.

The study noted that school closures typically flatten the peak of outbreaks but have modest effects on the eventual number of cases. Children who stay out of school have half the number of daily interactions with other children but are more likely to mix with children from other schools, the authors note. School closures also hamper the ability of health-care workers to go to work.

David Isaacs, a pediatrician and professor of infectious diseases at the University of Sydney, said closing schools may be unnecessary to limit the spread.

“Of course, anyone who is a bit scared will keep their children at home,” he said. “I don’t think that’s good for children and the whole of our normal living.”

Children appear to be at very low risk of severe outcomes from covid-19 if they do become infected with the coronavirus. Statistics updated Friday by the Centers for Disease Control and Prevention showed that in the United States from Feb. 1 to April 11, only three of the first 13,130 deaths officially attributed to covid-19 involved children under 15. From age 15 to 24, there were another 13 deaths.

Where are schools opening?

Norway’s schools reopen April 27 for grades one through four. Within the next three weeks, a host of other countries plan to follow for some students: New Zealand, Mexico, Germany and France are among them.

French President Emmanuel Macron said Monday that “there is an inequality in that there are those who don’t have Internet access and who can’t be helped by their parents.”

Israeli officials are considering the limited opening of some school programs for special education students before the end of April. Later, preschool, elementary, middle and high school programs would be phased in.

But the plan sparked a backlash from some parents. An Education Ministry spokeswoman said the ministry was moving with caution, looking at how to expand remote learning.

In China, some provinces reopened schools last month. Beijing and Shanghai have already reopened many businesses, but schools will come later: from April 27 to May 11.

Hong Kong, like mainland China and Macao, was among the first to close schools when the coronavirus hit, with widespread consensus that schools should close their doors, given the scars in Hong Kong society over the severe acute respiratory syndrome (SARS) outbreak in 2003 that took almost 300 lives in the territory.

Mickey Leung, an 18-year-old student in Hong Kong who will sit for a university entrance exam later this month, has to contend with the distraction of her brother playing computer games. Hong Kong schools remain closed.

“I find it really hard to concentrate at home. And on the other hand, anxiety over the virus has affected me psychologically, along with the constant changes in the date of the exam,” she said.

Singapore kept schools open until April 8, citing early data that showed children were less susceptible to the virus and had milder symptoms. But it changed course after covid-19 cases rose tenfold in a month.

In Russia, where new cases are rising swiftly, only 8 percent of schools are conducting classes in person.

Olga Ryazanova, whose son is in the ninth grade in Moscow, is worried.

“My opinion is that this situation will definitely have a negative impact on the quality of my child’s education. You need to have a strong will, high self-organization and motivation to study in this situation. Not everyone has that, unfortunately.

“It is the first time we’ve had this situation with a killer virus,” she added. “Everybody’s confused. So I wouldn’t dare to demand the opening of schools in this situation.”

Dixon reported from Moscow, Adam from London and Patrick from Sydney. Steve Hendrix and Ruth Eglash in Jerusalem, Shibani Mahtani and Tiffany Liang in Hong Kong, James McAuley in Paris, Mary Beth Sheridan in Mexico City, Joel Achenbach in Washington and Natasha Abbakumova in Moscow contributed to this report.