Secondary school and college pupils’ return to class in England will be staggered in the first week of January.

Exam-year students will go back to school as normal after the Christmas holidays, but the majority of secondary school pupils will start the term online.

It is hoped the staggered return will allow headteachers to roll out mass testing of children and staff in the new year.

But education unions are concerned about the logistics of setting up a mass testing programme and they have criticised the Government for making a last-minute announcement at the end of term.

Children in nursery and primary school will go back to class as normal in January, alongside students in exam years, key workers’ children and vulnerable pupils in secondary schools and colleges.

Guidance says all specialist settings and alternative provision should plan for full-time on-site provision for all pupils from the start of term.

But the Department for Education (DfE) has said secondary schools and colleges will offer remote education to all other students during the first week.

Face-to-face education for all students will resume on January 11.

In a written ministerial statement, Education Secretary Gavin Williamson said schools will be allowed to use an extra inset day on January 4 to prepare for the testing of pupils and staff at the start of the spring term.

Mr Williamson said: “This targeted testing round will clamp down on the virus as students return from the Christmas break and help stop the spread of Covid-19 in the wider community.”

It's just a complete dog's breakfast out there. Parents don't know from day to day whether their child is going to be in school

The announcement comes after Mr Williamson threatened legal action against Greenwich Council earlier this week after it advised schools to switch to remote education for most pupils in the last week of term.

Council leaders in Waltham Forest and Islington – who had also advised schools to move to online learning for the last few days of term amid rising coronavirus rates – were told to retract their advice.

When he was challenged on his decision to threaten councils with legal action, Mr Williamson told BBC News: “By taking these measures in secondary schools and colleges it means that we’re going to be able to maximise the amount of time children are in the classroom.

“And at every stage, we will take a robust and strong stance to ensure schools are open because as the Chief Medical Officer for England said that actually children are best in schools.

“It is the safest place for them to be. That’s why we continue to have a laser-like focus in terms of making sure children are in the classroom.”

Speaking to the Public Accounts Committee (PAC), Susan Acland-Hood, permanent secretary at the DfE, told MPs on Thursday that there were no “plans to lengthen the Christmas holiday”.

Meg Hillier, chairwoman of the PAC, said it was “ludicrous” that parents and schools still did not know, on the final day of term for many schools in England, what was happening on the week commencing January 4.

Speaking about events in London this week, Ms Hillier said parents had had “very confusing messages” from Government and local authorities and she described it as a “complete dog’s breakfast”.

Schools and colleges will be able to offer students two rapid tests three days apart on the first week of term as part of the rollout of testing.

Testing will be optional but strongly encouraged, particularly in areas of higher prevalence of the virus. Consent will be required from the student or parent.

The DfE has said guidance will be provided to schools and colleges shortly on how to set up and staff the testing sites.

Armed forces personnel will support through planning with schools and colleges and “reasonable” workforce costs will be reimbursed, it said.

In a written ministerial statement, Mr Williamson said: “Schools and colleges that opt in will need to provide a few members of staff to support the testing programme.”

Mary Bousted, joint general secretary of the National Education Union (NEU), said the Government’s announcement on the last day of term demonstrated “ministerial panic rather than rational and responsible action” in response to the rise in Covid-19 rates among pupils.

She said: “Armed with a 30-minute training video, they are being asked to administer tests to adolescents – who may have their own views about what is quite an invasive procedure.”

Dr Bousted added: “The presence of year 11 and 13 pupils on the school site at the same time as the testing arrangements and procedures are being put in place will be extremely problematic.”

This is a huge exercise requiring processes to be established and communicated, parental permission to be obtained, and doubtless innumerable other logistical issues to be overcome

Paul Whiteman, general secretary of the school leaders’ union NAHT, said: “By dropping this on schools minutes before the end of term, leaders are left with no time to implement Government’s instructions.”

He added: “Primary schools appear to have been completely ignored in this announcement. School staff and parents of younger children are rightly worried about transmission of the virus over Christmas and will struggle to understand why they are being treated differently.

“Once again, an announcement that, if properly planned and executed could have been positive, is poised to fail.”

Geoff Barton, general secretary of the Association of School and College Leaders (ASCL), said: “We are very concerned about the feasibility of setting up a testing programme at the scale envisaged.

“We welcome the limited support we understand will be available, but this is a huge exercise requiring processes to be established and communicated, parental permission to be obtained, and doubtless innumerable other logistical issues to be overcome.”

Secondary school pupils have among the highest infection rates, but early findings from a study suggest that the proportion of pupils and teachers with Covid-19 mirrors the proportion in the local community.

Of the 105 schools in England in the survey, 1.24% of pupils and 1.29% of staff tested positive for Covid-19 between November 3 and 19, according to the Office for National Statistics.

The survey also found that 27.6% of schools had one current infection, 27.6% had between two and five, and 44.8% had none.

Schools in Wales will also use staggered returns for pupils in January.

The new term will start on the fourth day of the month with online learning continuing for most learners, with face-to-face learning expected to return for most by January 11 and a full return before January 18.

Secondary schools and colleges in Wales moved to online learning on Monday in an effort to reduce the transmission of Covid-19.