The government is under pressure to change its guidance against using face masks in schools in England.
Head teachers want an urgent review of advice over face coverings in school and said if there is a u-turn it should be “sooner rather than later”.
Prime Minister Boris Johnson said, depending on the medical advice, “if we need to change the advice then of course we will”.
In Scotland secondary pupils will have to wear masks in school corridors.
In England, despite the official recommendations against using face coverings, some schools are already expecting pupils and staff to wear them.
The Oasis academy trust, with more than 50 schools in England, is providing visors for its teachers – and secondary pupils will have to wear masks in corridors.
On Tuesday, the ASCL head teachers’ union said parents and schools needed more clarity and “reassurance” over the evidence for not allowing masks.
The head teachers’ union said it would be “prudent” to reconsider the opposition to allowing masks, in the light of the policy in Scotland and the recent guidance by the World Health Organisation, which recommended face coverings for the over-12s.
The heads’ union asked what schools should say if teachers or pupils said they wanted to wear a face covering – and for a “clear direction one way or another”.
The union’s leader Geoff Barton also urged “if there is going to be any U-turn by the government that it does this sooner rather than later, because the start of the new term is imminent”.
On a visit to Devon, the prime minister emphasised the safety of the return to school in September, saying “all our scientific advice is that schools are safe, it’s absolutely crucial people understand that”.
On whether face masks should be allowed in school, Mr Johnson said: “We’ll look at the changing medical evidence as we go on, if we need to change the advice then of course we will.”
Despite the current guidance against using masks, it seems some schools are already making their own decisions.
Steve Chalke, chief executive of the Oasis academy trust, said there was a responsibility to make schools “as safe as we possibly can” – and that meant using masks and visors.
Like wearing a school uniform, he said wearing masks would become “part of what we do” and would be part of a wider safety plan, including hand washing and keeping pupils apart in separate “bubbles”.
But in secondary school corridors and shared areas, where pupils could not be kept apart, Mr Chalke said masks would be required.
“We’re using our common sense for our schools and our buildings,” he said.
It would help to protect teachers as well as pupils, he said, including those who might have underlying health conditions or who are in a more vulnerable age group.
Mr Chalke said schools leaders had to make a “moral choice” on how best to make schools safe on the scientific advice available.
He also thought using masks, which will be provided, might increase the confidence of parents “nervous” about sending their children back to school.
A secondary school in Kent, Sir Roger Manwood’s School in Sandwich, is expecting pupils and staff to wear masks – with pupils each being given three washable masks.
The government’s safety guidance, issued in July, says Public Health England does not recommend using face coverings in school.
As pupils would be in their own separate “bubbles” there is no need for masks, says the guidance, which warned that “misuse” of face coverings could “inadvertently increase the risk of transmission”.
Labour’s Shadow Education Secretary Kate Green called on the prime minister to “act quickly to give certainty to parents and teachers who are just days away from schools reopening”.
“There is a growing body of evidence that the use of facemasks in communal areas in secondary schools helps protect students and staff and drive down transmission,” she said.
A Department for Education spokeswoman said: “We have consistently followed Public Health England advice, which does not recommend the use of face coverings in schools because there are a range of protective measures in place, including children staying in consistent groups.
“We have set out the system of controls schools should use, including cleaning and hygiene measures, to substantially reduce the risk of transmission of the virus when they open to all children in the coming weeks.”