Delegates warned on Monday that the government's "reckless and simplistic" attitude to health and safety threatens to put the lives of children and adults in schools and colleges at risk.
A motion condemned the coalition's plans to remove vital health and safety protections in the workplace.
To support the debate an NASUWT report into excessive classroom temperatures was published.
The union has found that 93.7 per cent of teachers have experienced temperatures in excess of 24°C, while a third (33 per cent) have faced temperatures of over 30°C.
The survey is based on more than 1,000 monitoring forms by teachers, containing over 19,000 temperature recordings taken during four weeks last summer.
General secretary Chris Keates said: "NASUWT research has shown time and time again that teachers are facing serious health and safety risks in schools as a result of high levels of stress, school buildings which are outdated and not fit for purpose, the presence of asbestos and excessive classroom temperatures.
"Despite the weight of this evidence, since coming to power the government has slashed the budget of the Health and Safety Executive and announced plans to axe or reform 84 per cent of health and safety laws."