At least 820,000 children were off school due to Covid last week as pupil absences hit a record high since classes returned in March.
New figures reveal one in every nine state school pupils (11.2%) in England was stuck at home on July 8, up from 8.5% on July 1, and 5.1% on June 24.
Some 747,000 pupils were self-isolating due to potential contact with a case of coronavirus, of which 624,000 were sent home because of possible infection at school.
There were 35,000 pupils with a suspected case of coronavirus and 39,000 with a confirmed case of Covid-19.
The latest data reveals a massive surge in the number of pupils out of school, up from at least 620,000 on July 1 and around 375,000 on June 24.
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Shadow Education Secretary Kate Green accused the Government of sitting back to "let the Johnson variant rip, creating a crisis in our schools".
“Parents, pupils and teachers are crying out for help to keep children learning, but the Government are recklessly letting infections spiral," she said.
“We cannot simply wish away the real challenges of the pandemic, ministers should be supporting schools to get ventilation systems in place, providing NHS support to deliver testing and be taking responsibility by providing clear guidance on the wearing of face masks.”
Geoff Barton, General Secretary of the Association of School and College Leaders, said the increase in absence was evidence "the crisis in schools and colleges caused directly by the rules requiring teachers to send home large numbers of children to self-isolate who do not necessarily have the virus."
“The government’s decision to end this disruptive policy when the autumn term begins now heralds another huge set of challenges for education settings," he said.
"They need substantial support, both financially and practically, in setting up on-site asymptomatic testing for students when they return in September, installing high-quality air ventilation systems and in having robust outbreak management plans ready."
He called for an end to the "deafening silence" from the Government's vaccine advisers on whether children could get the jab.
“With just days left of the current academic year, school and college leaders need to know whether this is a possibility or not,” Mr Barton added.
Kevin Courtney, joint general secretary of the National Education Union (NEU), said: "Simply hoping for the best did not prevent the Delta variant breaching our borders, and hoping for the best will not be sufficient support for school and college leaders who need the backing of Government to stay open safely and sustainably when case counts rise.
"We can all hope for the best but we must plan for something that is less than the best."
