Currently, headteachers in England are being told that face maks will not be necessary in schools when they reopen next week as long as they adhere to hygiene rules.
But, in what could be another humiliating U-turn for the government after this year’s exams results fiasco, the PM has today said the guidance could be altered if the medical advice changed.
It comes after mounting pressure from both headteachers and unions who have called on the government to review its guidance on face coverings in recent days – although both Downing Street and ministers have said they had no plans to do so.
Speaking to reporters, Mr Johnson said: “On the issue of whether or not to wear masks in some contexts – you know, we’ll look at the changing medical evidence as we go on.
“If we need to change the advice then of course we will.”
He added: 'If there are things we have to do to vary the advice on medical grounds, we will, of course, do that.
“But as the chief medical officer, all our scientific advisers, have said, schools are safe.”
In Scotland, secondary school pupils over the age of 12 will wear face coverings in corridors, shared areas and on school buses.
First Minister Nicola Sturgeon said on Monday she was acting in response to new guidance from the World Health Organization.
The move was confirmed by Scotland's Education Secretary John Swinney who said secondary schools will be given 'obligatory guidance' that pupils should wear masks when outside the classroom from next Monday.
The Welsh Government also announced that it would decide tomorrow whether school children will be required to wear face coverings when they return to school.
Health Minister Vaughan Gething said he wants any change in guidance or the mandatory use of face masks or visors to be implemented before schools reopen on September 1, undoubtedly adding more pressure on Mr Johnson to now follow suit.