Pupils and teachers are being placed at risk because proper health and safety rules are not being followed in schools, a survey suggests.
By Hannah Goff
BBC news at the NASUWT conference in Belfast
Four out of 10 of the 5,000 heads and teachers polled said their employers did not carry out regular checks.
The survey for the NASUWT union found many schools were not tackling asbestos and that one in four did not carry out the required fire drills once a term.
The results of the survey were released at the union's conference in Belfast.
General secretary Chris Keates said the results revealed a disturbing picture of "catastrophic failures waiting to happen".
Teachers and pupils were being put at risk, she said, adding that far more stringent sanctions needed to be put in place to ensure guidelines were properly followed.
'Welfare of pupils'
She added: "It's a growing concern that some schools seem to think that they are immune from implementing the law of the land.
"This is not just a workforce issue - it's an issue for the welfare of pupils as well."
Some 73% of teachers polled said an asbestos hazard was not properly marked, 51% said it was not properly contained and 79% said there was no proper plan in place for its removal.
And 94% of teachers said they had been required to work in excessively hot temperatures - without access to drinking water in a more than a third of cases.
And 83% had also worked in excessively cold temperatures during the winter.
Despite increased investment in school buildings the survey suggested that nearly half of schools had leaking roofs, a third were damp and one in three had slippery corridors.
Ms Keates vowed to pursue a campaign to ensure employers were fulfilling their health and safety obligations with "renewed vigour".