Schools are struggling to remain open due to rising Covid-19 cases resulting in staff and student absences, an education association said.
According to Association of School and College Leaders (ASCL), schools in high infection areas in England have had 25% of staff absent over three weeks and called on the government to offer schools financial backing for supply covers.
Figures released from the Department of Education estimate that nationally 2.4% of teachers and school leaders in open state-funded schools were absent due to Covid-related reasons on 9 December up from 2.0% at the end of November.
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Pupil figures also showed a decrease in attendance.
On Thursday December 9 the figures estimate that 236,000 (2.9%) pupils were absent from school for Covid-related reasons, compared to 208,000 pupils (2.6%) on Thursday, 25 November.
3,000 pupils were out of school as a result of school closures, which was the same on 25 Nov when there were 1,000 school closure cases.
Last week Health Secretary Sajid Javid said that he was not ruling out closing school if a fresh wave of infections is severe enough, and warned that home learning could return if the Omicron variant spreads drastically.
But some educational trusts have taken the decision to close up early ahead of the Christmas holidays due to high infection rates in the area, and move to home learning - including a primary school and secondary school in Suffolk.
Currently, Boris Johnson's Plan B announcement brought little changes into schools, with children still required to attend in person and no requirement to wear masks in classrooms or corridors.
Children aged 12 to 18 are all being offered vaccines, but there is no plan yet to extend the vaccination programme to primary school aged pupils.
ASCL general secretary Geoff Barton said that it was "no surprise" that the statistics showed a increase in pupil and teacher absence because of Covid-19 - but warned for schools the "challenging" times were still to come.
"The situation has clearly been deteriorating through the course of this half term with many schools and colleges experiencing huge disruption," he said.
"The Omicron variant threatens to unleash even more difficulties. The forthcoming Christmas holidays will at least provide a firebreak but there can be little doubt that the spring term will be challenging.
“Schools and colleges have worked immensely hard throughout the course of this very tough term, and throughout the entirety of the pandemic, to keep education going as best they can in these turbulent circumstances. But the unrelenting pressure has been absolutely brutal. Education staff deserve huge credit for everything they have done and are doing."
Mr Barton also called on the government to back up schools with more support in terms of Covid t esting, ventilation and more assistance with the financial cost of supply cover.
He also told the government that schools need to be communicated with over any new plans and measures in connection with the Omicron variant "promptly and clearly."
Mr Barton told BBC Radio 4's Today Programme that one school has emailed him stating that 25% of staff have been off for three weeks.
"You can imagine if you can't then get supply teachers, that becomes very difficult to maintain the quality of education, " he said.
Regional education body Schools North East said that Covid-related disruption has been a "major challenge" for schools in the region, with large numbers of students and staff absent - and conformed that staff absences impacting on the ability of schools to remain fully operational.
A spokesperson for Schools North East said that according to a survey they conducted based on 200 schools in the North East, just over half of schools had staff attendance levels below 90%.
The majority of schools had student attendance above 90%, however over 40% were below this.
Crucially, over three quarters said that attendance levels were below what they usually are in November.
A spokesperson for Schools North East said: "Recent data from the Department for Education highlighted the increasing number of staff and students absent due to Covid, and schools in our region have also reported absences relating to other illnesses.
"Keeping schools operational has been difficult, with several schools having to close year groups due to staff shortages.
"Schools have found it difficult to get cover staff, stretching staff workload, increasing stress and worsening mental health. Staff are anxious that with increasing Covid cases, they may find themselves having to isolate over the Christmas holidays."
The spokesperson said that schools have had to manage this disruption while supporting students with "catch-up" and "wider emotional wellbeing."
"Schools have gone ‘above and beyond’ acting as the ‘fourth emergency service’ during the pandemic," they continued. "This has often been done without clear guidance from central Government.
"Considering the role schools play as national strategic infrastructure, it is vital that the Secretary of State protects schools."
The Labour party this week also called on the government to 'act now’ to prevent chaos for schools in the new year.
Kevin Courtney, Joint General Secretary of the National Education Union, said rolling out Covid-19 vaccinations to "as many eligible children as possible" in the next couple of weeks, as well as ensuring that all adults can access their booster, will help minimise disruption to children's education.
Mr Courtney also said there needed to be a focus on testing and ventilation saying, "The Government has already squandered so many opportunities to improve ventilation in schools and right now that task is more urgent than ever."
