The prime minister has tonight suggested that schools may not reopen to pupils next term according to the government’s new timetable after all.

Asked whether students’ staggered start return dates in January were guaranteed, Boris Johnson said: “Obviously, we want, if we possibly can, to get schools back in a staggered way at the beginning of January in the way that we’ve set out.

“But obviously, like you expect, the commonsensical thing to do is to follow the path of the epidemic and, as we showed last Saturday, to keep things under constant review.”

Coronavirus: Unions to back schools that refuse mass testing plan

Nick Gibb: Teachers won’t have to carry out mass tests

Staggered term start: Most secondary school students will learn online in the first week of term

News: New Covid variant may infect pupils ‘more effectively’

He added: “It is very very important to get kids and keep kids in education if you possibly can. I believe that’s something everybody understands.”

Coronavirus: School reopening plans ‘under review’

The leaders of the NEU teaching union wrote to Mr Johnson today to call for all secondary students to be kept at home - except key workers’ children and vulnerable pupils - over the first two weeks of January in order to allow teacher vaccination and mass testing to be set up.

Last week, the government announced that most secondary school and college students’ return to class in England would be staggered in the first week of January to help schools roll-out mass testing of students.

But scientists have suggested that the mutated coronavirus strain could more easily infect children.

When asked whether he could guarantee that schools would be back on the planned start dates, Mr Johnson said: “The most useful thing I can tell you at this stage is obviously we want, if we possibly can, to get schools back in a staggered way at the beginning of January in the way that we have set out.

“But obviously … the commonsensical thing to do is to follow the path of the epidemic and, as we showed last Saturday, to keep things under constant review.

“It is very, very important to get kids and keep kids in education if you possibly can.”

On Sunday, health secretary Matt Hancock refused to confirm that schools in Tier 4 areas would reopen in January if cases continue to rise, saying: “I’ve learned not to rule anything out in this pandemic.”

Asked about schools reopening in Tier 4 on Monday, the PM’s official spokesman said: “No change … it’s rightly been a national priority for all pupils to return to school full time.”

School leaders have condemned the government’s plans for a mass testing regime for secondary students in January as “undeliverable”.