Hull City Council wrote to parents at St Mary’s College to say that Year Nine pupils should stay at home for the rest of the term because “a very small number of cases have shown an indicator on the PCR sample which is often, although not always, linked to the omicron variant”.

The council’s director of public health said further tests would be done to confirm the variant but would take a few days, adding: “With Christmas approaching and a rising number of cases we want to stop the opportunity for further spread as quickly as possible.”

Arabella Skinner, a director of the parent campaign group UsForThem, said the Government’s “confused” guidance meant children were being “penalised” by missing time in the classroom.

She said: “The Department for Education needs to get a grip on making sure that face-to-face education is a priority. It sounds like these panicked responses from local public health officials are not proportionate and are not putting children first.”

Year Four classes at Lime Tree Primary Academy in Sale, Trafford, have been told to stay at home until the end of term following a suspected omicron case.

Phoenix Collegiate, in West Bromwich, has also closed its doors until January following one confirmed case of omicron, and Hampton Primary has sent home Year Three following a positive case.

Elsewhere, schools started to draw up lists of key workers’ children in preparation for January. A primary school in Wiltshire said it “think it is wise to plan in the unlikely event of school closures”, as it asked parents to submit their job details so it could update its critical workers register.

Thomas’s London Day Schools, a group which runs several prestigious private schools in London including Thomas’s Battersea, which is attended by Prince George and Princess Charlotte, is also making plans for remote education in January should the Government mandate it.

A well-placed source said: “The board is currently drawing up plans to prepare for remote working. Discussions have been ongoing in recent weeks and an announcement is likely to be made shortly.”

A spokesman for the group said that “like all schools Thomas’s runs continuous contingency planning in line with Government advice on Covid”. He added that this is “standard contingency planning which covers many possible elements in this constantly changing situation”.