Reintroducing masks in schools has emboldened teachers to "go rogue" and cancel classes, MPs have been told.
Pupils in Year 7 and above are being asked to cover their faces in communal areas and on school transport, amid a tougher Government measures to tackle the omicron variant of Covid-19.
However, the House of Commons education select committee heard on Wednesday that the renewed face mask recommendations are likely to spur on headteachers to impose further restrictions which go beyond official guidance.
This means that the imposition of masks is unlikely to reduce school closures due to Covid-19 outbreaks, but make it more likely that pupils will be sent home by overcautious staff if a pupil tests positive for the virus.
Miriam Cates, a Conservative MP and education committee member, told the meeting: "Unfortunately, the effect of imposing the mask mandate again has not been to give schools a sense of relief that they’re being protected, it’s actually been that they go further – start cancelling nativities, isolating children.
"I’ve got pages and pages and pages of examples sent by parents across the country of schools not following Department for Education guidelines, that are going well beyond – closing schools, isolating children they shouldn’t be.
“Introducing masks again has had the opposite effect and is more likely to close schools, because it’s given schools the sense that they can now go further.
"What is the department going to do to make sure schools stick to the letter of the guidelines and don’t go rogue?"
Headteachers under pressure to ‘introduce all sorts of crazy things’
Will Quince, Minister for Children and Families, responded: "We don’t want to be overly prescriptive. I appreciate what you’re saying and I hear about it too – there are schools cancelling nativities and I find that deeply regrettable."
Speaking after the meeting, Ms Cates added: "There’s nothing wrong with the guidelines, but the trouble is that headteachers are under pressure from unions to go well beyond and introduce all sorts of crazy things.
“If we were talking about education, of course we should give headteachers autonomy, but this is public health. Why are we expecting them to make scientific and public health decisions? We should not be allowing schools to deviate from the guidelines."
Robert Halfon, who chaired the meeting, questioned Mr Quince over the mandating of face masks in schools but not in offices.
He added: "We allow people to go to nightclubs and bars, yet schools are closing down nativity plays or putting them online.
"Why is it that I can go to a nightclub but whole groups of children are sent home, nativity plays are being cancelled yet people can go and mix in bars?
"Why is it that masks are not compulsory in offices, yet children are being told to wear them in school corridors? Why is there one rule for children, and one rule for everybody else?"
Mr Quince said: "I accept the points raised about masks and the very limited evidence as to their efficacy," but said that the mask-wearing rule was a "proportionate measure".