Teachers across France staged a one-day strike on Thursday to protest changing Covid testing rules which they say have disrupted lessons and are now too lax to protect against the tear-off Omicron variant Across the country.

Many teachers’ unions have also planned protest marches, one of the largest due to start in Paris on Thursday afternoon. The education ministry said nearly 40 percent of primary teachers and almost a quarter of secondary teachers are on strike, although unions believe the numbers are much higher.

The ministry did not say how many schools were closed for the day, but one of the largest unions said it expected around half of primary schools to close due to the walkout.

The stop-work action, backed by most of the country’s teacher unions, has posed a serious challenge to the government of President Emmanuel Macron, which is proud to keep its schools open longer than many other European countries for the pandemic.

“I fundamentally believe that the choice we made to keep schools open is the right choice,” Macron said at a press conference on Tuesday.

But the policies put in place to keep schools open come at a cost. The government has put in place complex testing rules designed to prevent entire classes from being sent home or entire schools from having to close for a small number of positive cases. Authorities then changed the rules twice in a matter of days, confusing millions of parents and teachers. Testing protocols have led to meandering lines of exasperated parents and children standing in the cold outside pharmacies and medical labs.

To stave off a growing wave of anger, Prime Minister Jean Castex said on Monday that the protocols would be relaxed. Parents would no longer have to pick up their children immediately after a classmate tested positive, and exposed children would no longer need to be tested in pharmacies and labs to return to class. Instead, the tests could be done at home.

But teachers said the simplified rules increased the risk of infections at school. They have also been complaining for weeks about a lack of equipment such as air quality monitors and a shortage of highly protective masks.

“They threw the doors of the school wide open at Omicron and made a mockery of the teaching staff,” a union of principals said. wrote on Twitter Monday after Mr. Castex’s announcement.

France now has on average nearly 300,000 new cases of coronavirus reported per day, nearly six times more than a month ago and far more than at any time prior to the pandemic. Olivier Véran, the country’s Minister of Health, said on Thursday that he had tested positive for Covid-19. Mr. Véran, who is fully vaccinated, said on twitter that he would self-isolate and work remotely. “

The surge in Covid infections has resulted in the closure of more than 10,000 classrooms in France, and tens of thousands of students are currently infected, according to French authorities.

The walkout, which was expected earlier in the week, “demonstrates the growing desperation in schools,” Snuipp-FSU, the main union for primary school staff, said in a statement on Tuesday. “Not only does the current protocol fail to protect students, staff and their families, it also completely disrupts schools,” the statement said.

Although teachers’ strikes are common in France, they often do not unite as many unions as Thursday’s action. A large parents’ federation also called on parents to walk alongside teachers.