TORONTO (NYTIMES) - Most stores were shut. Barber shops and salons shuttered. Restaurants and bars - including the outdoor seating where hardy souls had braved meals under heat lamps - were banned. Gyms, pools, even the beloved hockey arenas were closed in the strictest shutdown Toronto has confronted since the pandemic's first wave last spring.

Except for the schools.

Facing a resurgence of coronavirus infections in Toronto, the fourth largest city in North America retreated back into lockdown on Monday (Nov 23), along with two booming suburbs. But in contrast to New York and other big American cities, officials are finding it more beneficial to keep schools open.

"We cannot put in class learning at risk," Ontario's premier Doug Ford who is ordinarily an advocate for business, said last Friday when announcing the closures.

Along with trying to avoid overwhelming the hospitals and to protect the elderly in long-term care homes, Mr Ford said, schools were "what matters most."

Mr Ford's announcement illustrated how Canada has followed the lead of much of Europe, prioritising the opening or reopening of schools, while just across the border many US states have focused on keeping businesses such as bars, restaurants and gyms at least partially open.

Since schools resumed classes in September across Canada after, in some cases, many months of remote learning, there has been strong enthusiasm to keep them open.

In most places there are no official thresholds for shutting schools down and there is little appetite to do so, according to Mr Ahmed Al-Jaishi, a public health researcher who is part of an academic team compiling school outbreaks across the country.

And, despite fears among parents that students would bring the disease home and among teachers that they would get infected in large numbers, such outcomes have been rare.

"The good news is that we're not seeing much evidence of transmission within the schools," said Dr Barbara Yaffe, Ontario's associate medical officer of health.

Even so, a significant minority of parents in Toronto, at least, have been reluctant to allow their children to return to in-class learning, particularly now, as the city is seeing the greatest surge of the virus since it arrived.

Last week the city reported a 6.2 per cent positive test rate - meaning that for every 1,000 people tested, 62 are infected. That is more than double the 3 per cent positive test rate in New York that triggered school shutdowns last week.

"We expect staff and students to be contagious, and come to school with infections. But the measures we have in schools have so far been effective at preventing the additional spread," said Dr Vinita Dubey, Toronto's associate medical officer of health.

Most schools across the country shut in March, when Prime Minister Justin Trudeau asked Canadians to stay home and closed the border. In many cases, the schools didn't reopen until September, after months of parental complaints, children falling behind in schoolwork and rising concerns about the effects of social isolation.

By then, the chorus of concern was met by growing scientific evidence that time outside of school was more dangerous to children than the risk of going back into classrooms.

A report by Toronto's Hospital for Sick Children released this summer called for a full return to school, stating that while children under 10 were less susceptible to the virus and less likely to pass it onto others, they were already reporting increased rates of depression and anxiety. Experts said they believed that substance abuse and suicidal behaviour went up as well.

That was followed by a study in August, published in the Canadian Journal of Public Health, detailing a sobering list of long-term effects on young children who miss school, from less-developed cognitive skills and higher incidences of teen pregnancy to lower employment rates and higher arrest rates.

"You can close restaurants and bars and give financial handouts so they can reopen at a later date," said Dr Michael Silverman, the chair of Infectious Diseases at Western University's School of Medicine & Dentistry in London, Ontario, who co-authored that report. "What kind of financial handout can you give to a kid for the long-term cognitive development impacts, to make up for it?" He added, "Schools should be the very last thing to close."

As a vast country with strong regional governments, back-to-school plans in September varied nationwide. For instance, in Quebec all elementary and high school students were required to attend classes in person, with masks required for grade 5 and up. In Alberta, children could return to school physically, or continue to attend online.

However, when schools opened in Toronto in September, about 30 per cent of elementary students and 22 per cent of secondary students in the public school system decided to attend virtually. Since then, those numbers have substantially risen, indicating persistent parental fears despite the expert assurances.

"There's a reason why a very large percentage of parents and guardians chose not to have their kids in schools," said Dr Charles Pascale, a professor of applied psychology and human development at the University of Toronto and a former deputy minister of Education in Ontario. "That's the best evidence the school reopening in Ontario was a disaster - mainly because their parents were concerned the safety precautions were not enough."