Worst affected by the five-month absence are children in the most deprived schools as well as pupils from Bame (black, Asian and minority ethnic) backgrounds, found the National Foundation for Educational Research.
Labour said the report should be a “wake-up call” to Boris Johnson and education secretary Gavin Williamson, who risk “failing a whole generation of children” unless they provide the support needed for the class of 2020 to catch up.
Sir Keir Starmer has called on Mr Williamson to come before the House of Commons to explain how he will protect children’s futures.
“He needs to explain how he will make up for the damage already done, bring pupils up to speed and mitigate against the ongoing risk from the pandemic,” said the Labour leader.
Labour is calling on Mr Williamson to delay GCSE and A-level exams scheduled for May 2021 in England by up to two months to June or July, in order to give pupils time to make up for lost learning.
Exam regulator Ofqual is currently consulting on the possibility of putting the dates back by a matter of weeks, and Mr Williamson confirmed that later exams were an option, though aides stressed that no decision has yet been made.
The education secretary told the Daily Telegraph: "I know there's some concern about next year's exams... Ofqual will continue to work with the education sector and other stakeholders on whether there should be a short delay to the GCSE, A-level and AS-level exam timetable in 2021 with the aim of creating more teaching time."
Some 97 per cent of schools in England and Wales are expected to open their doors to all pupils over the next few days, with the remainder – about 700 schools – phasing the return in with a “transitional period”.
Most pupils will find themselves divided into year-group bubbles to limit the spread of Covid-19 and will experience staggered arrivals and lunchtimes. Head teachers will have discretion over the use of face coverings outside the classroom, and they will be mandatory in communal areas of schools in local lockdown zones.
Mr Williamson paid tribute to the work of teachers and other staff in preparing for the return: “I do not underestimate how challenging the last few months have been but I do know how important it is for children to be back in school, not only for their education but for their development and well-being too.
“It is down to the sheer hard work of so many teachers and school staff that from today pupils will be able to learn in their classrooms together again. It has not been easy for parents nor schools, but we could not have got to this point without your support and I cannot say thank you enough for this.”
But nearly all – 98 per cent – of teachers surveyed for the NFER report felt their students were behind where they would usually expect with their curriculum learning at the end of the last school year.
As of July, respondents said they had covered about two-thirds of the curriculum on average during the last academic year, amid the disruption caused by coronavirus.
Teachers surveyed estimated on average their students were around three months behind expectations in July, the NFER said.
However, more than half – 53 per cent – of those teaching in the poorest schools in England reported their students were “four months or more” behind in their learning, compared to 15 per cent of teachers in wealthier settings. And the proportion of children needing intensive catchup support was also higher in schools serving areas with high numbers of youngsters of Bame backgrounds.
The survey also found that the learning gap between disadvantaged pupils and their better-off peers had increased by 46 per cent, adding that the figure was likely to be an “underestimate”.
The majority of pupils had been expected to learn at home throughout the 2019-20 summer term, but teachers reported that only 38 per cent returned their last piece of set work in July, compared to 42 per cent in May.
Almost one-quarter – 21 per cent – of teachers from across more than 2,200 mainstream primary and secondary schools also believed boys had fallen further behind than girls.
The survey asked nearly 3,000 school leaders and teachers in England about how pupils had coped with their learning after schools shut for most of them in March due to coronavirus.
Some year groups were allowed back in the classroom from the start of June, while vulnerable children and those with key worker parents have been allowed in school throughout the pandemic.
Dr Angela Donkin, chief social scientist at NFER, said: “Whilst it is crucial that children catchup, we should not assume that teachers will immediately be able to deliver the same quality of teaching, at the same speed, as before the pandemic.
“There remains a range of barriers for teachers and schools, which means catchup should be seen as part of the ongoing process of learning recovery, for most pupils, rather than as a quick-turnaround solution.”
She said it was “clear” that additional support needed to be targeted at disadvantaged pupils and schools in the poorest areas.
The Department for Education spokesperson said: “While the attainment gap had narrowed since 2011, many pupils have had their education disrupted by coronavirus, and we cannot let these children lose out.
“That’s why throughout the pandemic we have invested in remote education, providing devices, routes and resources for the children who need them most, and why our £1bn Covid catchup package will tackle the impact of lost teaching time – including targeted funding for the most disadvantaged students.”
Steve Chalke, the founder of the Oasis Trust chain of academy schools, said that delaying exams was “a bit of a red herring”.
Children facing exams in 2021 effectively only have two terms of teaching left, he said.
“We have the autumn term and the spring term, we have got to pack in so much teaching that has been missed in that time to get children up to speed,” said Chalke.
“To delay the exams doesn’t take away from the issues we’re facing. What we need from the government and Ofqual is an end to uncertainty.
“Every student and every teacher deserves a clear baked-in fail-safe timetable and plan that takes on board all of the disruptions that may occur through the year and has some built-in contingencies.
“These exams and the grades that young people get at GCSE and A-level, if they are wrong, if they messed up, they deal a huge blow to young people’s life chances.”
Meanwhile, unions called on the government to temporarily scrap fines for parents who do not send their children back to class due to fears around coronavirus.
Local authorities can fine parents £120 – cut to £60 if paid within 21 days – over a child’s absence from school, with the threat of prosecution if they fail to pay.
The National Association of Head Teachers (NAHT) said while it hoped attendance would be “as close to 100 per cent as possible”, it understood “there will be some families who do not yet feel ready to return”.
General secretary Paul Whiteman said: “If you are a parent and you are worried about safety, a fine is unlikely to make you feel any safer.”
The National Education Union joint general secretary, Mary Bousted, said fining families for school absences “will not resolve the fears or anxieties felt by many”.
The Department for Education (DfE) said fines for parents who refuse to send their children to England’s schools will only be used as a “last resort” when classes resume.
School term start dates vary across the country, with approximately 40 per cent expected to start term today and others following over the coming days. Schools in Scotland and Leicestershire have already opened.
The new school term follows the unanimous backing for a full return from the chief medical officers across the four nations of the UK, who said the health risk posed by Covid-19 to children is extremely low and noting the significant risk to young people’s well-being if they are not back in school.
Additional reporting by PA
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