More than four-fifths of headteachers (83%) have said they do not have enough money to maintain their school buildings.
In a survey by the National Association of Head Teachers (NAHT), just 5% of school leaders said they had enough money to ensure buildings met pupils’ needs.
Funding for school buildings has been cut by 50% in real terms since 2010, just as many buildings are reaching the end of their life cycle, the NAHT said.
The union called for an extra £4.4bn a year to upgrade school buildings.
General secretary Paul Whiteman said: ‘In the last year, while the RAAC crisis has grabbed headlines, hundreds more school buildings have quietly slipped further into disrepair.
‘Our children deserve to learn in safe, comfortable conditions.
‘With a General Election on the horizon, I urge all political parties to commit to a long-term plan backed up by serious new investment to ensure all school buildings are safe and fit for purpose.’
