The government has been urged to introduce a maximum permitted temperature for schools as England sees record-breaking heat this week.

Unions have called on the government to set a limit on how hot schools can be after the country experienced the hottest May day on record yesterday, with London temperatures exceeding 35C.

Currently there is no legal limit for how hot - or cold - workplaces can be, with employers expected to ensure that temperatures are “reasonable”.

However, unions say that setting temperature thresholds should be considered, now that warmer summers are becoming the norm.

Impact of heat in exams season

Pepe Di’Iasio, general secretary of the Association of School and College Leaders, said the introduction of a maximum working temperature is worth considering.

“There are already issues with schools overheating in the summer months, and these will only increase as temperatures continue to rise,” Mr Di’Iasio warned.

His concerns were echoed by Daniel Kebede, general secretary of the NEU teaching union.

“A maximum working temperature for schools would encourage investment into making schools heat-resilient, with mitigations such as air conditioning, which would protect learning, the important exam period, and keep staff and children safe and comfortable,” Mr Kebede said.

Research by the Department for Education in 2025 found that an estimated 6.7 days of learning were lost each year as a result of heat. Concerns have also been raised about temperatures during summer exams.

Paul Whiteman, general secretary of the NAHT school leaders’ union, said that schools were doing all they could to mitigate the effects of high temperatures.

This included making “straightforward adjustments such as limiting the time spent in the sun during breaks, ensuring additional water is available, making adjustments to uniform expectations where appropriate, and ventilating classrooms as best they can”.

In December 2024, advice from the UK Health Security Agency stated that schools should “consider rearranging school start, finish and play times to avoid teaching during very hot conditions”.

Schools were previously forced to shut during the 2022 heatwaves, despite the DfE advising against this.

Urgent call to improve school buildings

Unions told Tes that one of the biggest causes of hot classrooms is the quality of the buildings.

Mr Di’Iasio said: “A big part of the problem is that ageing school buildings often have poor ventilation, leading to uncomfortable conditions that can result in lost learning.”

He urged the government to invest more in the school estate to make these buildings fit for the future “in a way that mitigates extreme temperatures as much as possible”.

Additional investment has been planned through the DfE’s 10-year estates strategy, including measures to prevent overheating.

However, Mr Whiteman said that the government needs to “act more urgently to improve and modernise school buildings”.

This includes “a focus on ventilation and, potentially, air conditioning”, he added, as “school buildings need to be conducive to learning all year round”.

Maximum temperature proposed

Last week the Climate Change Committee published a report that advocated for maximum temperature regulations in workplaces, including schools.

“Maximum working temperature regulations would address the increasing risks that high temperatures pose to workers’ safety and incentivise the deployment of the necessary cooling,” it says.

The report, A Well-Adapted UK: the fourth independent assessment of UK climate risk, also calls on the government to invest in cooling for key public services.

By 2050, the committee recommends, temperatures of indoor learning environments should remain between 16C and 25C.

It also recommends that the government improve its understanding of the impact of extreme weather. This includes the number of weather-related school closures and the number of staff unable to attend work due to extreme weather.