Hundreds of thousands of pupils will not return to schools and colleges as planned due to rising infection rates and the spread of the new Covid variant.

Announcing a U-turn on the planned staggered reopening, Education Secretary Gavin Williamson said students in exam years will return to secondary schools a week later than planned, from January 11.

Other secondary and college students will go back full-time on January 18, he told Parliament.

And primary schools in a “small number of areas” where Covid-19 infection rates are the highest will not reopen for face-to-face teaching to all pupils as planned next week.

Shadow further education and universities minister Emma Hardy said it was a “shambles” that a list of schools had not been provided alongside the Education Secretary’s statement.

A list of the areas where it is expected that some primary schools will not open as planned next week to all pupils was later published by the Department for Education and featured London, Essex, Kent, East Sussex, Buckinghamshire, and Hertfordshire.

There has been growing concern from teaching unions and scientists about the spread of the virus following the discovery of its much more transmissible variant, with rising case rates and hospital admissions in many parts of the country.

Mr Williamson told MPs in the Commons that the Government had to make an “immediate adjustment” to its plans for the reopening of schools in early January.

He said: “We must always act swiftly when circumstances change. The evidence about the new Covid variant and rising infection rates have required some immediate adjustment to our plans for the new term.”

He added: “The latest study we have from Public Health England is that Covid infections among children are triggered by changes in the community rate. The study also says that the wider impact of school closures on children’s development would be significant.

“I’m quite clear that we must continue to do all we can to keep children in school.”

The staggered approach was due to see primary school pupils and Year 11 and Year 13 pupils returning in the first week of January, and other students going back later in the month to allow headteachers to roll out mass testing of children and staff.

Wednesday’s change of plan comes after warnings from experts suggesting a delayed return might be necessary as hospitals struggle with more Covid-19 patients than in the peak of the first wave.

Mr Williamson said the Government expects to deliver 50,000 devices to schools across the country on January 4, to support remote and online learning, adding that 100,000 devices in total will be delivered during the first week of term.

Geoff Barton, general secretary of the Association of School and College Leaders, said the decision to delay face-to-face teaching for secondary pupils is “unsurprising”, adding the “difficult balancing act” between keeping education fully open and suppressing the virus “has clearly swung in the direction of tackling the immediate public health crisis”.

But he said concerns remain about the “huge logistical challenge” of recruiting and training staff to run mass testing centres for secondaries and colleges.

Mr Barton, who said Government has “made a habit of chaotic eleventh-hour announcements which leave schools and colleges picking up the pieces”, said the support being provided for mass testing remains insufficient and that discussions with ministers and officials on improving it will continue.

Paul Whiteman, general secretary of the National Association of Head Teachers (NAHT) described the announcement as “another last-minute mess which could so easily have been avoided” had the Government listened to school leaders before the Christmas break.

He said: “Instead, back then, schools which wanted to shift to remote learning were threatened with legal action. Now we have a situation where the Government is instructing schools to reduce the amount of teaching time available.

“If we’d had the freedom to take action before the holidays, we might have been in a position to have more schools open for more pupils. School leaders will be baffled, frustrated and justifiably angry tonight.”

Universities are also being asked to reduce the number of students returning to campus from the beginning of next month, Mr Williamson said, adding that students who need practical learning to gain their professional qualifications should be prioritised.

He said all university students should be offered two rapid coronavirus tests on their return to campus.

Alistair Jarvis, chief executive of vice-chancellors’ group Universities UK, said it was “right that Government and universities should look again at plans for the start of the spring term” given the changing situation with infections in recent weeks.

He added: “Today’s announcement will understandably raise further issues and uncertainty, for students, universities and staff, which will need to be addressed by Government over the coming weeks, including the need for financial support, regulatory flexibility and assessment changes.”

A YouGov poll conducted overnight suggested that 43% of 7,999 British adults would “strongly support” keeping schools in England closed for two further weeks after the Christmas break.

Just 9% “strongly oppose” and 10% “somewhat oppose” keeping school gates shut, YouGov said.