Headteachers have warned that schools face a “recipe for chaos” after experts predicted an “exponential” rise in Covid infections among pupils returning to the classroom in the new term.

New documents published today reveal that the government was warned by its own scientific advisers earlier this month that it should prepare for a “high prevalence” of the coronavirus in schools by the end of September.

Launching the government’s “Back to school and college” campaign this week, education secretary Gavin Williamson said the start of the autumn term would mark “the point when our focus can shift away from the disruption of Covid and on to learning, enrichment and recovery”.

Scientific advice: DfE told to prepare for high Covid rates in schools

New term: Schools ‘could keep masks and social distancing’

Revealed: 4 in 5 teachers not reassured by carbon-dioxide monitors

But in its latest consensus statement on Covid-19, dated 11 August but made public today, the government’s Scientific Advisory Group for Emergencies (SAGE) warns that it is “highly likely that exponential increases will be seen in school-attending age groups after schools open”.

The Association of School and College Leaders (ASCL) said the findings were “extremely worrying”, while the NEU teaching union said the statement served as a “rebuke to Gavin Williamson”.

Covid in schools: ‘The situation is on a knife edge’

Julie McCulloch, ASCL director of policy, said: “It is extremely worrying to see scientific advisers concluding that exponential increases of coronavirus infections are highly likely in school-age children and demonstrates that the situation is on a knife edge as the new term approaches.

“We simply cannot have another term of disruption and it is vital that the government is ready to respond rapidly to any upsurge in infections with more support for schools and colleges.

“The government has published a contingency framework which maps out a series of measures in response to outbreaks of coronavirus.

“But there is a real danger that this will become the normal state of affairs with various measures being implemented on a local basis.

“This is clearly a recipe for chaos, and the government cannot once again allow a situation to develop in which attendance unravels, and children experience yet more disruption. It would also be helpful to hear from the JCVI [Joint Committee on Vaccination and Immunisation] sooner rather than later about the possibility of offering vaccinations to 12- to 15-year-olds.”

Kevin Courtney, NEU joint general secretary, said: “This statement from SAGE is a rebuke to Gavin Williamson.

‘Next to nothing has been done’ to prepare for large numbers of Covid cases

“Next to nothing has been done to prepare for the possibility of large numbers of cases, which will lead to lots of education disruption as children and staff have to isolate because they are positive - or stay off because their Covid symptoms go on longer.

“It is only right to recognise that a large percentage of the school community is unvaccinated, and that this will remain the case for a while yet. We cannot just assume a return to normal from the start of term. The bringing together of a school community of several million will inevitably lead to a rise in case counts.

“During the summer term, Gavin Williamson was conspicuous both by his absence and his silence, when cases were riding so fast in schools. It is perfectly clear to education professionals that the current safety requirements for schools and colleges are not sufficient to prevent a rise in cases come September.

“The CO2 monitors are welcome but far too late - contracts have not even been assigned for them yet. And they will be rolled out over many weeks, and will only diagnose a problem, not solve it.

“To prevent a sharp rise in cases, the watchwords must be ventilation, air filtration, masks, vaccines and vigilance.

“Gavin Williamson needs to support schools to consider face coverings from day one of term, alongside social distancing where possible, and special consideration for vulnerable staff.

“The danger is not that schools and colleges will be slow to act, but that government is.”

A Department for Education (DfE) spokesperson said: “Education remains a national priority, and the plans for autumn will make sure schools and colleges deliver high-quality, face-to-face education to all pupils with minimal disruption. We know that being out of education causes significant harm to educational attainment, life chances, mental and physical health.

“Thanks to the success of the vaccine programme, we are able to return closer to a normal education experience for the autumn term.

“The measures in place strike the right balance between making schools safe with enhanced ventilation, Covid testing and vaccinations of older students and staff, and reducing disruption by removing bubbles and face coverings.”