Labour are demanding the government publish scientific evidence to support the return of schools and colleges, as ministers come under further pressure to delay the return of pupils to classrooms.
Under current government plans, primary schools and Year 11 and Year 13 students in secondary schools will return from their Christmas holidays next week.
Other children will go back a week later, as part of a staggered schedule.
However, teaching unions are among those calling for the return of schools and colleges to be delayed, as the UK deals with record numbers of coronavirus infections and COVID patients in hospitals.
Education Secretary Gavin Williamson was seen in Downing Street on Monday.
And Number 10 said on Tuesday it was "still planning for a staggered opening of schools" after Christmas with new testing programmes.
But the prime minister's official spokesman also added: "We have said throughout the pandemic, we obviously keep all measures under constant review."
Boris Johnson will chair a meeting of senior cabinet ministers on Tuesday evening to consider new coronavirus measures, ahead of a review of England's tiered restrictions due on Wednesday.
The COVID-O meeting - expected at 6pm - will look at whether regions should move tiers and is also likely to look at the issue of keeping schools shut for longer.
Labour's shadow education secretary Kate Green and shadow schools minister Wes Streeting have written to Mr Williamson to demand the government publish advice from the Scientific Advisory Group for Emergencies (SAGE) on the return of schools in January.
On Monday, the Politico website reported SAGE - led by the government's chief scientific adviser Sir Patrick Vallance - had urged ministers to keep secondary schools closed next month in a bid to dampen the rise in infections.
It comes after a recent paper on the new COVID variant by the London School of Hygiene & Tropical Medicine warned that even action similar to November's second national lockdown across England - in which schools remained open - is "unlikely" to reduce the rate of infection to below one "unless primary schools, secondary schools, and universities are also closed".
Ms Green said: "The government cannot continue to hide from reality and must urgently publish the scientific advice on the return of schools.
"Parents, pupils and staff are incredibly concerned about what will happen next week, with the prime minister governing through media leaks rather than evidence and clarity.
"The government has lost control of the virus and children's education is suffering as a result.
"It's time for the prime minister to own his mistakes and be honest about whether students can return to schools and colleges in a week's time."
A member of the government's New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG), which has been analysing the new COVID variant that has taken hold in England, warned the country was "entering a very dangerous new phase of the pandemic".
There is evidence the new variant is more infectious than the original coronavirus strain.
Andrew Hayward, professor of infectious diseases epidemiology at University College London, told BBC Radio 4's Today programme: "We're going to need decisive, early national action to prevent a catastrophe in January and February.
"A 50% increase in transmissibility means that the previous levels of restrictions that worked before won't work now, and so Tier 4 restrictions are likely to be necessary or even higher than that.
"I think we're really looking at a situation where we're moving into near lockdown, but we've got to learn the lessons from the first lockdown."
Prof Hayward suggested that allowing pupils to return to schools would mean stricter restrictions in other areas of society.
His fellow NERVTAG member, Professor Neil Ferguson admitted that keeping schools shut "may be required at least for a period" as the new variant meant there was "less wiggle room" for keeping control of infection rates.
Senior Conservative backbencher, Sir Roger Gale MP, is among those calling for a delay to schools returning after the Christmas holiday.
He told Sky News: "The state of the health service suggests the situation has changed very dramatically since decisions to send children back to school were taken some weeks ago.
"There is no shame whatsoever, in light of a changing circumstance, to change the plan.
"Given the strain on the health service, given the situation we face in schools and the knowledge that we now know that young people will catch and spread the disease, we have to take the delay.
"Preferably, I'd like to see that delay maintained until priority is given to teaching staff so they can be vaccinated as well."
Geoff Barton, general secretary of the Association of School and College Leaders (ASCL), proposed the number of pupils in schools could be restricted while testing systems - which the government has pledged military support for - are put in place.