The rise in homeschooling could "seriously derail" catch-up efforts, the chief inspector of Ofsted has warned, as she says that not every parent is "equipped" to be a teacher.
While many parents "gladly stepped back" from teaching duties when schools reopened, some have chosen to keep their children at home, according to Amanda Spielman.
She said that a disproportionate number of the youngsters who have not returned to the classroom following lockdown have some kind of problem or need.
She will tell the Association of Directors of Children’s Services online conference on Friday that referrals of children to social services are only just returning to pre-pandemic levels.
"That’s a lot of missing referrals, and some of them would have been of children suffering significant harm," Ms Spielman will say.
"And then there are the children who haven’t yet returned to school. The Centre for Social Justice reported that almost 100,000 children were still out of school last December. This fits with what we heard in our school visits last autumn.
"Many parents have gladly stepped back from teaching duties, but some have kept their children at home. But for many children there is so much ground to make up, and not every parent is equipped to be a teacher. This could seriously derail the catch-up effort."
Ofsted published a report last autumn which found that more than a third of schools saw an increase in children being home educated at the start of the academic year.
Headteachers reported that the rise in parents pulling their children out of school since the start of the new academic year is down to their "anxiety" about Covid-19.
Children ‘used as buffer against infection’
Ms Spielman will say that the vast majority of parents are responsible and competent, but it is the minority who are not that she is concerned about.
She will also use her speech to welcome the end of bubbles, adding: "Children do just need to be in school."
Ms Spielman will warn that children continue to experience disruption to the school day.
She will say: "We’ve all seen the recent steep rise in absences – around 1 in 20 children out of school because of Covid. Of course, the vast majority haven’t got Covid, but are still being forced to miss out on school.
"We seem to have carried on using children as an infection buffer for a very long time, given what we know about the risks to them and the risks they pose to others."
On Friday, the Department for Education (DfE) will announce a new £10 million scheme aimed at helping disadvantaged children catch up with maths and English. The cash will be used to train school staff to deliver special maths lessons for pupils in Year One, Year Two and Year Seven, as well as phonics lessons for primary school children.
A new website for parents will also be launched on Friday by the DfE to highlight the different catch-up support that is available for particular age groups.