Any relaxation of the requirement for face masks to be worn in secondary schools must be based on “clear scientific advice”, headteachers have warned following reports that the prime minister is set to announce a lifting of the rule on Monday.

While unions are keen not to see masks in classrooms any longer than necessary because it “hampers communication”, there are concerns about the risk of spreading Covid-19 if the requirement is lifted.

Education secretary Gavin Williamson has said the government plans to remove the requirement for face mask wearing for secondary students in England. Boris Johnson is expected to make the announcement on Monday.

Gavin Williamson: School mask rule set to end despite teacher opposition

Unions: Don’t ‘rush’ to remove student face masks

Nick Gibb: Masks-in-class rule will lift in mid-May if data allows

The lifting of the measure is anticipated to happen at step three of the government’s roadmap out of lockdown, which will be no earlier than 17 May.

Face masks ‘an essential part of Covid control in schools’

The move comes despite a group of unions and scientists writing to the government calling for face coverings to remain in schools until at least 21 June, saying the measure is “an essential part of the wider system of control in schools”.

The proposals have led to mixed feelings among teaching unions, particularly as not everyone has received one or both doses of the coronavirus vaccine as yet.

“It is obviously better for communication and learning if we don’t need to have children wearing face masks in classrooms,” said Geoff Barton, general secretary of the Association of School and College Leaders (ASCL).

“But we know there will be concerns among some staff and parents about the risk of infection, and it is important to remember that not everyone has received the Covid vaccine yet, or a second dose of the vaccine.

“Any relaxation of face mask rules must be guided by clear scientific advice, and we would expect this to be kept under review in the event of an increase in cases.”

Mr Barton called for greater clarity from the government so schools and colleges know exactly what to do and if they have any leeway.

“What we want to see from the government is clarity in the guidance that is given to schools and colleges over this matter so that everyone knows where they stand and there aren’t grey areas left to negotiate,” he added.

“It’s important that it’s very clear what schools and colleges are required to do, and where they have discretion to make decisions based on their own contexts and risk assessments.”

Paul Whiteman, general secretary of school leaders’ union the NAHT, said that highlighting the reasoning behind the decision to the public is paramount.

“No one wants to see face masks in classrooms for longer than they are necessary,” he said.

“Creating the confidence that this next step is the right thing to do is essential to avoid an unnecessary shock to a system in recovery.

“Parents, pupils and staff will want to understand why removing the requirement for face coverings in classrooms is considered appropriate when it is not for other enclosed spaces.

“We expect that school leaders will continue to work closely with their staff and communities and make decisions based on their risk assessments and local circumstances.”

Kevin Courtney, joint general secretary of the NEU teaching union, said he was “disappointed” the government had not taken the advice expressed by unions and scientists in their letter.

“As we understand it, the prime minister will say it will no longer be mandatory to have face masks worn in classrooms.” he said.

“We think mask wearing has become accepted and feel there was a good reason to look at the data for longer after other restrictions in society were lifted on 17 May and if cases still continued to fall, then that would have been a better time to lift the school face mask measures.”

Mr Courtney added that he could see the temptation to lift the measures but that there is good evidence that mask wearing inhibits the transmission of the virus, and he believes many schools will continue to ask for face masks to be worn, even when it is no longer mandatory.

“It is important that we all do everything we can to keep coronavirus cases going down,” he said.

“We gave the government some advice; they have not taken that advice and we are disappointed.”

Jon Richards, head of education at Unison, which represents school support staff said:  “It would be unwise to abandon a sensible and successful approach on masks this soon.

“The Government should hold off until next month.

“New concerns over Covid variants and some increase in school infections show more caution is needed. It’s better to be safe than sorry and put staff, pupils and the community at risk.”