Some primary school pupils in England will not return to school on 4 January.
Education Secretary, Gavin Williamson, made the announcement on Wednesday 30 December, following very high rates of infection in the south of the country.
The start of term will also be delayed for many secondary schools in England.
Here’s everything you need to know about when schools could go back in January.
Why will some primary schools not go back?
Most primary schools in the country will return for the new term on Monday 4 January.
However, schools in “at-risk” Covid areas in the south of England will now not reopen for most pupils until 18 January, in a bid to curb the spread of the virus.
The closures will be reviewed every two weeks.
Gavin Williamson said 85 per cent of primary schools would still reopen for pupils on the original new term date.
Speaking to BBC Breakfast on 31 December, the education secretary said he wanted the school closures to be “as short as possible”.
Explaining why only some primary schools in England would close despite surging cases across the country, Mr Williamson told Sky News: "The work that was done with the Department of Health who identified areas where it was either a very high rate or, using their latest data, were seeing very sharp increases in the number of cases or equally the pressures on hospitals in that area and the clinical needs.
"These were all the considerations that were taken into account but what I want to say, and this will come as no surprise to you whatsoever, I want to see schools, any school, that’s closed for those first two weeks, opening at the earliest possible opportunity."
Some parents and teachers have voiced complaints about the short notice given before term was due to begin.
Addressing the concerns, Mr Williamson said: "I think we all recognise that if we go back a few weeks where there was no new variant of Covid, none of us would have been expecting us to be having to take the actions, whether it’s in regards to schools, whether it’s in regards to Tier 4 moves that the Government has had to make, but it’s the Government that’s having to respond at incredible pace to a global pandemic and then a new variant of that virus.
"It’s not what any of us would want to do, it’s not a decision that any of us would be wanting to have to implement, but we’ve had to do that because circumstances have dictated it.
"I think the British public expect the government to do what is right and even though that is sometimes uncomfortable, it is taking the right actions, dealing with these extraordinary times."
What about secondary schools?
There will be a staggered return for secondary school pupils in the new year, in order to set up mass testing.
Pupils taking exams in 2021 will now go back to school on 11 January, while other year groups will return on 18 January.
Speaking on BBC Breakfast, the education secretary said remote learning would be “mandatory” from 11 January for all secondary school students, except those in years 11 and 13, who will go back to classrooms on that date.
Vulnerable children and children of key workers will still go back to school on the original new term date.
Boris Johnson has hinted that these plans could still change, depending on the spread of Covid-19.
"I want to stress that depending on the spread of the disease it may be necessary to take further action in their cases as well in the worst affected areas," he said.
Gavin Williamson said he was confident that schools would be ready to administer Covid tests to the pupils returning to face to face learning from 11 January.
He pointed to £78 million of additional funding, equipment such as personal protective equipment (PPE) and support from the military to help schools to set up mass testing programmes quickly.
Which school areas will be affected?
According to the Press Association, these are the areas where it is expected that primary schools will not open as planned next week to all pupils:
London - Barking and Dagenham, Barnet, Bexley, Brent, Bromley, Croydon, Ealing, Enfield, Hammersmith and Fulham, Havering, Hillingdon, Hounslow, Kensington and Chelsea, Merton, Newham, Redbridge, Richmond-Upon-Thames, Southwark, Sutton, Tower Hamlets, Waltham Forest, Wandsworth, Westminster
Essex - Brentwood, Epping Forest, Castle Point, Basildon, Rochford, Harlow, Chelmsford, Braintree, Maldon, Southend on Sea, Thurrock
Kent - Dartford, Gravesham, Sevenoaks, Medway, Ashford, Maidstone, Tonbridge and Malling, Tunbridge Wells, Swale
East Sussex - Hastings, Rother
Buckinghamshire - Milton Keynes
Hertfordshire - Watford, Broxbourne, Hertsmere, Three Rivers
When will schools reopen?
A decision on when closed primary schools should reopen “will obviously be guided by the public health advice,” Gavin Williamson said.
The education secretary said schools would be closed for a two-week period before a review would determine whether pupils can return.
“After the two-week period there will be a review. Our obvious hope and desire is to see that those areas that are in the contingency frameworks would be moving out of that,” he said.
“We will obviously be guided by the public health advice and the scientific advice that is available to us.”
What are other UK nations doing?
The other UK nations have different plans for schools returning in the new year.
In Scotland, the Christmas holidays were extended to 11 January, and the week after will be remote learning only.
A full return to face-to-face learning for pupils is planned for 18 January.
In Wales, teaching is due to start in most places from 4 January, but with “flexibility” in place.
Schools are expected to reopen for face-to-face learning for most pupils by 11 January, with a full return by 18 January.
And in Northern Ireland, schools are currently scheduled to open as usual, even though the nation went into lockdown after Christmas.