Tory ministers have been condemned after schools were ordered to close just days before the end of the summer holidays as they are not safe for pupils.
The move came after it emerged the concrete used to build them - known as RAAC - is at risk of collapse.
More than 100 schools will have to either partially or completely close as a result of the safety scare.
Education secretary Gillian Keegan said the government was taking a “cautious approach” to protect pupils and staff.
She said: “Children should attend school as normal in September, unless families hear differerently.”
But her Labour shadow, Bridget Phillipson, said: “This is an absolutely staggering display of Tory incompetence as they start a fresh term by failing our children again.
“Dozens of England’s schools are at risk of collapse with just days before children crowd their corridors. Ministers have been content to let this chaos continue for far too long.
“It’s long past time the Secretary of State got a grip on her department. Labour knows that children can’t get a first class education in a second class school, it’s incredible that the Tories don’t.”
Mike Short, head of education at the UNISON union, said the situation was “nothing short of a scandal”.
He said: “The Department for Education and government have squandered valuable months hiding this crisis when they should have been fixing dangerous school buildings.
“The schools minister even broke his own promise to publish information about at-risk properties before parliament’s summer recess.
“Parents, pupils and staff will be relieved the issue is finally being taken seriously. But to wait until the eleventh hour as schools are preparing for a new academic year will create turmoil for thousands of families. And this could just be the tip of the iceberg.”
Gillian Keegan said: “Nothing is more important than making sure children and staff are safe in schools and colleges, which is why we are acting on new evidence about RAAC now, ahead of the start of term.
“We must take a cautious approach because that is the right thing to do for both pupils and staff.
“The plan we have set out will minimise the impact on pupil learning and provide schools with the right funding and support they need to put mitigations in place to deal with RAAC.”