Secondary school students should have to wear masks in classrooms as well as communal areas in the weeks after a "circuit-breaker" lockdown, according to the Independent SAGE group.
The group of scientists has called for schools to be closed for up to three weeks in a circuit-breaker lockdown around half-term and for masks in classrooms to be part of a package of national measures to slow the spread of the virus when schools return.
The government's own official SAGE (Scientific Advisory Group for Emergencies) group recommended a circuit breaker last month, but this advice has not been followed by Boris Johnson's government.
The Independent SAGE Group has produced a six-week emergency plan, which would start with a circuit-breaker lockdown for two to three weeks.
It then calls for masks be worn in classrooms and communal areas of secondary schools for another three or four weeks after the lockdown.
Independent SAGE committee member Dr Zubaida Haque said: "Masks are already worn in corridors in schools, but, given lack of space to socially distance in the classroom, we think this will be needed for a finite amount of time after a two-week national circuit breaker.
Coronavirus: 'High rates of transmission' among older teenagers
"This would allow us to stem and manage the spread of the virus, particularly given high rates of transmission among older teenagers and sixth-formers."
The Independent SAGE group's emergency plan says that after schools return from a circuit-breaker, some national measures would be needed to keep the R rate – the coronavirus reproduction rate – below 1.
This includes masks in secondary classrooms, closure of leisure and hospitality sectors and all university teaching being moved online unless face-to-face classes are absolutely essential.
The group highlighted its plan during a briefing on schools. A member of the public asked why, if masks were required in shops and on trains, they were not being worn in school classrooms. They said: "Giving how much we know about how the virus spreads, it seems that putting 30 teenagers, without masks, in a stuffy classroom seem the worst possible arrangement in terms of viral transmission."
Dr Haque said: "We have suggested in our plan that once we finish with a two-week circuit breaker, with new restrictions when children go back to schools, secondary school children we have recommended should wear masks."
Independent SAGE member Dr Christina Pagel, professor of operational research at UCL, said that holding a circuit-breaker lockdown now could help to save lives in December.
She said that Covid-19 deaths were now doubling relentlessly every two weeks. Prof Pagel warned that this was likely to continue in November and that people who will die of the virus next month will likely already have got the virus.
She said that if cases continue to double, we could be looking at 6,000 more deaths by 19 November and added that “there is not much we can do about it.”
“But if we can reduce transmission now, like right now, then we can save lives by 3 December and that is really what the circuit breaker is about.”
She presented a graph on the projected reduction in Covid-19 cases if a circuit breaker was introduced now or in two weeks' or four weeks' time.
The Department for Education said earlier this year that wearing masks in schools was not recommended.
However, following a U-turn, it has now said that masks should be worn in the communal areas of secondary schools and colleges in areas classed as high risk or very high risk for Covid-19 transmission.