Live Updates: Spain Warns of High Death Toll in Heat Wave

Extreme heat is broiling much of western Europe, but class is still in session for millions of students in countries such as Britain and France, where few schools are air-conditioned. The heat has trapped education officials between trying to avoid school closures, which mean lost learning days, and the effects of high temperatures, which research shows can affect learning outcomes and test scores.

Until relatively recently, many European schools were somewhat protected from extreme heat because classes were mostly out by summer’s peak. British and French school years end in July, later than most U.S. schools but still before the most sweltering weeks of August.

Climate change is hitting Europe hard, and it is getting hotter sooner in the year. That means more intense heat at the end of the school year, with students often in aging buildings made to insulate against the cold, not keep cool in the heat.

“You’re putting kids in a greenhouse for six hours a day,” said Pete Lynch, the principal at Sheldon School in Chippenham, southwestern England. His state-funded school closed early on Tuesday and will stay closed on Wednesday and Thursday.

But, Mr. Lynch said, he had no alternative. The windows open no more than a crack. The school has only a few air-conditioning units, some of which cool servers, and there are just 50 fans for 60 classrooms, 20 of which he bought last week.

“The buildings aren’t designed for heat,” he said. “They aren’t designed for anything, really. When it’s cold, it’s freezing.”

Although the problem has worsened in Europe in recent years, schools have struggled to adapt.

Paris is buying 1,200 air-conditioning units to give out to 620 preschools and elementary schools, according to Mayor Emmanuel Grégoire. By Monday, the city had deployed just 150. In schools that have stayed open, teachers were loosening uniform rules to allow for cooler clothes and canceling gym classes.

Violaine Guéguen, who teaches in a Paris preschool, said the heat was almost unbearable. Parents were carting their own fans back and forth. The principal covered windows with blankets to keep rooms darker, and the faculty filled toy boxes with water and let students play with it in a shaded part of the courtyard outside.

“We can’t go on like this, constantly having to find D.I.Y. solutions ourselves,” Ms. Guéguen said. “We are bound to face more heat waves.”

The Belgian authorities issued a heat warning for most of the country from Wednesday until Friday, with temperatures set to exceed 35 degrees Celsius, or 95 Fahrenheit.

Several schools decided to suspend afternoon classes until the end of the week, while others are staying open but are replacing lessons with cooling activities such as outdoor water games, said David Janssens, a spokesman for the public education network of the Flemish Community. To escape overheated classrooms, one primary school, in the municipality of Hoegaarden, moved some classes to the air-conditioned conference rooms of local businesses, Joris Verbaeten, the mayor of Hoegaarden, said in a social media post on Monday.

The dilemma of whether to close schools has divided parents, teachers and education officials, resurrecting the polarized debates of schooling during the coronavirus pandemic.

“Obviously, it’s unsafe for them to be here,” said Emma Hergest on Tuesday, as she sprayed sunscreen onto the necks of her children — ages 9, 8 and 5 — before they went to school in London’s 92-degree heat.

On Monday, the British Department for Education said it did not recommend school closures for the heat. “School attendance is the best way for pupils to learn and reach their potential,” the department said in a statement. “And hot weather can usually be managed safely.”

Many school leaders have to make their own calls.

In France, nearly 10,000 of the country’s 60,000 schools closed or changed their schedules this week because of the heat wave, Édouard Geffray, the education minister, told lawmakers.

Britain has no similar tally, the education department said in an email, but local news reports, school announcements and interviews with parents suggested that many schools were at least partly closing.

Closures have left many parents struggling to find child care even though homes or other settings may not present a better option for staying cool. “Who has air-conditioning in London?” said Dr. Silvia Pierini, a pediatrician in the city.

Adult supervision is an argument for keeping classes open, she said. “At least in school, there is control.”

Some parents have shrugged off the alarming headlines and heat warnings, saying they grew up in hotter places.

“It does make you laugh — kids go to school around the world,” said Claire Demetriou, 39, who has family in Greece.

Sofia Georgieva, 36, said she might need to find child care for her 7-year-old daughter. “When it’s too hot, there’s just no point to be there,” Ms. Georgieva said. “There’s no learning.”

But as a hairdresser, she added, she won’t get paid unless she goes to work. If school closed, she said, it left her with “a really tough decision.”

She would not be able to regularly take off work, she said, and she does not see officials or school leaders making real plans to prepare for extreme temperatures.

That feels like a structural problem, she said: “This country is not designed for the heat.”

Koba Ryckewaert contributed reporting from Brussels.