Boris Johnson has insisted that it is “prudent” to stick to the planned March 8 opening date for schools in England, despite coming under pressure from his own MPs to speed up the process.
The Prime Minister said the proposed date was three weeks after the most vulnerable should have been vaccinated, giving time for immunity to kick in.
But in Scotland, First Minister Nicola Sturgeon has said schools will begin a phased reopening from February 22.
Elsewhere, the Welsh Government is due to make a decision by the end of the week on whether to reopen schools after the February half-term.
But Mr Johnson said at the Downing Street press briefing on Wednesday that the Government would be sticking with its own “cautious” approach.
“What we don’t want to do now that we are making progress with the vaccine rollout and we have got a timetable for the way ahead, we don’t want to be forced into reverse,” he said.
“We think this is the prudent and cautious approach. I think it is much better to stick to that.”
Chief medical officer for England Professor Chris Whitty said schools in England had been managing to “hold the line” and remain open up until the new, more transmissible variant of the virus hit.
“The rates are now coming down but they are still incredibly high,” he said.
“If we were to start take-off again from the very high levels we are at the moment, the NHS will get back into trouble extraordinarily fast.”
But Prof Whitty said schools are a safe place for children to be.
He said it was up to ministers to decide the opening dates for schools but that he was confident the risk to children of getting Covid-19 is “incredibly low”.
Earlier on Wednesday, former chief whip Mark Harper, chairman of the Covid Recovery Group, reiterated his call for the Government to ease lockdown restrictions as soon as possible.
Tory MP Mr Harper said in a statement: “The Prime Minister said last week that reopening schools was a ‘national priority’.
“Now that Scotland has indicated that schools are likely to return from February 22, there needs to be a very good reason for keeping English schools shut for so much longer.”
He urged the Government to start easing all restrictions from March 8, adding: “We’ve got to demonstrate to the public how the good news about the vaccination rollout translates into a return to normal life.”
Ms Sturgeon announced on Tuesday that schools in Scotland would begin a phased reopening from February 22, and said this date would be subject to final confirmation in two weeks’ time.
In Wales, negotiations with trade unions are continuing this week in the hope of being able to make an announcement on schools reopening on Friday, Welsh Government minister Eluned Morgan said on Monday.
A phased return to the classroom, starting with primary school children, could begin after the February half-term break if Covid-19 cases continue to fall in Wales.
Ms Morgan, minister for mental health, wellbeing and Welsh language, said: “We are absolutely determined to reopen schools as early as possible and that’s why there will be intensive discussions with unions this week to make sure that we can put all of the things in place so that we can ensure the safety, as far as possible, of the students and teachers.”
Ms Morgan told a Welsh Government briefing that First Minister Mark Drakeford has already said he wants to give parents, pupils and teaching staff two weeks’ notice before a phased return begins.
The PM has named February 22 as the date the Government will publish its “road map” for the easing of lockdown restrictions in England.