More than 150 in England must immediately shut buildings made with a type of concrete that is vulnerable to collapse until safety measures have been implemented, the government has announced.
The schools have been contacted by the Department for Education (DfE) ahead of the start of term - which is next week for most pupils.
Some schools will have to relocate children to other classrooms or makeshift areas as a result of the discovery of the potentially crumbling concrete.
Safety measures include propping up ceilings in buildings made with reinforced autoclaved aerated concrete (RAAC).
The Department for Education has not given a timeline for replacing the RAAC, but school leaders have called for an “urgent plan” to fix buildings.
Roughly 50 schools had already been made aware of the problem while a further 100 were alerted this week. The DfE has not released the details of the schools to be hit by the closures.
Some schools’ leaders have accused the government of being too slow in addressing the problem.
A report in June assessed the risk of injury or death from a school building collapse as “very likely and critical”. The DfE has emphasised that in many cases it is onle one classroom or building on a school site that has the concrete and the rest of the school can operate normally.
Education Secretary, 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”.
The DfE added that schools will be goven assistance in finding alternative spaces after the closures while every schoool will have a case worker to aid them as they tackle the problem.
School trust chiefs warned the timing of the announcement “couldn’t be more disruptive” and called on the Department for Education (DfE) to make sure its response was “as strong as possible”.
Confederation of School Trusts chief executive Leora Cruddas said: “This is a very serious situation and it couldn’t be more disruptive at the start of a new academic year.
“However, children’s safety must come first so the government is right to proceed with caution.
“It is absolutely imperative that the operational response from the DfE is as strong as possible and that this gets schools and trusts the help they need in this extremely challenging circumstances.”
Association of School and College Leaders policy director Julie McCulloch said the Government had been too slow to respond.
She said: “The danger of structural failure in school buildings where this type of concrete was used in construction has been known since at least 2018.
“The Department for Education’s own annual report last year identified the condition of school buildings as one of six ‘significant risks’ it was managing, describing this risk as ‘critical – very likely’ and ‘worsening’.
“It has taken the Government far too long to act on a risk of this seriousness.
“The scramble now taking place to contact affected schools ahead of the imminent start of the new school year is clearly vital, but the actions these schools will need to take will be hugely disruptive, and this will obviously be worrying for pupils, families and staff.
“The Government should have put in place a programme to identify and remediate this risk at a much earlier stage.”
Teaching unions have also been critical of the government.
The Unison public service union’s head of education Mike Short said: “This situation is nothing short of a scandal.
“The DfE 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.”