Nearly 4,000 schools in England are in need of immediate restoration work, government data shows.
And many more schools lack paperwork – required by law – relating to building safety, it has been reported.
Figures from a government programme assessing the condition of its schools estate show that 3,731 have buildings with "elements" – such as roofs, walls or windows – that require immediate replacement or repair.
Labour's shadow education secretary Angela Rayner said schools across England were in "dire need" of repair, but funding was not available.
"That failure to invest has left our children and hard-working school staff at risk, trying to teach in buildings that are crumbling around them," she added.
The data, obtained through freedom of information (FOI) requests by the Guardian newspaper, was collated by the Department for Education's school condition data collection programme, which was launched in 2017.
Information was released for 21,796 schools, of which 1,313 had elements that were given the lowest possible condition rating, defined as a "life expired and/or serious risk of imminent failure", the newspaper reported.
It said 705 schools had more than two elements given the worst condition rating, while 69 had more than 10.
Meanwhile, in a survey by the NEU teaching union – published in November – 47 per cent of 670 members said their school or college buildings were "not fit for purpose".
A further 21 per cent said parts or all of their buildings had been closed due to disrepair over the past five years, according to the NEU.
FOI data further revealed that 2,939 schools did not have an asbestos management plan, 2,717 did not have a fire risk assessment, 2,215 were lacking a gas safety test report and 2,098 did not have an electrical test certificate.
The Department for Education toldThe Guardian that in some cases the documentation could have been held off-site by multi-academy trusts managing the schools.
Kevin Courtney, NEU's joint general secretary, said: "It makes no sense for important practical documents, required by law, not to be held on the premises of a school or college.
"The reason the government gives – that they may be held by a multi-academy trust – would be laughable if it weren't so serious. If they are missing, how can the risk be safely managed?"
Responding to the findings, schools minister Nick Gibb said: "The Conservative government provides money annually to improve the condition of school buildings.
"In this academic year, over £1 billion has been made available. We also recently announced a £400 million fund for schools to improve their buildings."