Head teachers have complained about a lack of clarity over the rules on whether teachers or pupils can wear face masks in schools in England.
They want to know if they can override the official guidance which rejects the use of face coverings in school.
"The guidance is silent on what schools should do if staff or pupils want to wear face coverings," says Geoff Barton of the ASCL head teachers' union.
A Downing Street spokesman ruled out any review on masks in school.
First Minister Nicola Sturgeon said on Monday she was acting in response to new guidance from the World Health Organization.
But Mr Barton said it remained unclear whether schools in England could have flexibility to allow masks if they were requested as a safety measure by teachers or pupils' parents or where they might be seen as a "useful additional measure".
It comes as head teachers in England have written a letter to Education Secretary Gavin Williamson, seen by the Guardian, accusing the government of failing to listen during the coronavirus crisis.
The Worth Less? lobbying group, which says it represents thousands of head teachers, wrote that they felt they were "working in isolation" from the government as they faced "some of the most important challenges of our professional lives".
"Collaboration, consultation and partnership have felt in short supply and this caused immense frustration as time, energy and resources have been wasted by head teachers as we respond to shifting policy directives and myriad changes," it said.
Jon Richards of Unison, representing support staff in schools, said masks were worn in other workplaces and it was "vital" that school staff should be allowed to wear them.
Medical advisers at the weekend also highlighted the risk of teachers spreading the virus to each other - rather than from pupil to pupil.
The government's guidance, issued in early 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".
On Monday, a Downing Street spokesman said masks could get in the way of communication between teachers and pupils.
Since the government guidance was published on returning safely to school on 2 July, the use of masks has become more widespread, for example, becoming compulsory in shops.
ASCL said they had asked for further guidance on wearing masks more than a month ago.
"It would be helpful if the government could provide more advice on these complex issues but that has not been forthcoming," said Mr Barton.
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."