Why heatwaves pose a hidden threat to schools

When heatwaves have hit the UK recently, discussion about the impact on schools has largely focused on maximum classroom temperatures and maintaining acceptable conditions to keep schools open.

But there is another dimension to the hot weather that a growing number of campaigners are pointing to as an issue: higher pollution levels in the air around our schools.

According to the National Centre for Atmospheric Science (NCAS), air pollution levels are closely linked to the weather, and heatwaves “often arrive hand-in-hand with poor air quality”.

“With climate change making heatwaves more likely, we must consider the different ways that rising temperatures will affect us, including the air we breathe,” Dr James Allan, NCAS’ lead scientist for air pollution research, said in an interview for the NCAS website.

Climate change may be making the situation worse, but children’s exposure to dangerous levels of air pollution from traffic, among other sources, is an existing challenge.

So, just how big is the problem?

A 2021 study published in Environmental Research modelled air pollution concentrations alongside monitoring data to estimate how many schools in England were located in areas where the pollution exceeded the World Health Organisation’s (WHO) recommended annual mean limit. The researchers found that around 7,800 schools in England were in this category. This was more than a third of schools, serving more than 3.3 million pupils.

The scientists also found a strong correlation between the schools with higher air pollution levels and the number of students on free school meals and from ethnic minority backgrounds. They called for increased focus on this issue, pointing to the fact that some of England’s most vulnerable children were being exposed to the highest levels of pollution.

But the problems don’t end there. The Guardian reported last year that “almost nine in 10 planned new school sites exceed three WHO targets on air pollution - and all breach at least one of them”.

How pollution affects health and learning

All of this matters because the impacts of air pollution on children’s health are manifold. The charity Asthma and Lung UK lists asthma, coughing, wheezing, pneumonia and increased risk of lung cancer or COPD (chronic obstructive pulmonary disease) as key concerns.

Jemima Hartshorn, co-founder of action group Mums for Lungs, says that “in 2024, in London alone, nearly 114,000 children went to hospital struggling to breathe”, adding that while “not all of these cases were because of air pollution, [many were] worse because of it”.

There is also increasing evidence that pollution has a bearing on cognitive function - and therefore on pupils’ ability to learn.

Mike Gilraine, an assistant professor in the economics department at Simon Fraser University in Canada, used evidence from a huge gas leak in Aliso Canyon, California, to assess the effects of pollution on attainment. In his paper, he explains how “the offending gas company installed air filters in every classroom, office and common area for all schools within five miles of the leak (but not beyond)”. The pollution in classrooms with filters was reduced to nothing, but not so in classrooms outside of this area, offering a chance for direct comparison.

His findings show that “air filter exposure led to a 0.20 standard deviation increase in mathematics and English scores, with test score improvements persisting into the following year”.

An author of multiple papers on this topic, Gilraine says that while the evidence of physical and cognitive impacts is mounting, awareness is still dangerously low. He argues that “the academic literature now includes enough studies establishing a causal link between air pollution and student test scores that we can now characterise the relationship as causal rather than correlational”.

That body of evidence includes research carried out by Sefi Roth, associate professor at the London School of Economics and Political Science (LSE), who studied the effects of indoor air pollution by looking at “administrative data on 2,418 students taking 11,443 exams at a leading public research university within the Greater London urban area”. His finding backs up Gilraine - being above the WHO’s guidelines for pollution levels reduced test scores by 13.5 per cent.

Help for schools?

So what is being done? The government released guidance on ventilation in schools in February this year. It states that schools should “regularly monitor ventilation and air quality across your buildings”.

The Department for Education says it has provided all state-funded education and care settings with carbon dioxide monitors. Just over 8,000 schools were also provided with free-standing high-efficiency particulate air (HEPA) filtration units in 2021-22, but this was largely prompted by the Covid-19 pandemic. The scheme has now closed, and the DfE notes that it will not pay for repairs, replacements or new filters.

As things stand, if schools want to improve the quality of the air in their classrooms, they need to fund this themselves.

According to Gilraine, the most cost-effective method for improving indoor air quality is using air filters, such as the units provided to schools during the pandemic.

This, he says, “is a much more feasible lever for improving student outcomes over a focus on outdoor air pollution”. Carbon-dioxide monitors can help senior leaders decide which spaces to target with filters first, Gilraine adds.

A start-up called Vox Aeris is hoping to reduce the operational costs associated with air purification systems further. However, the venture is focusing on commercial and industrial applications first.

Schools taking action

In the absence of financial support to bring down indoor pollution levels, some schools have opted to take action by signing up to initiatives to reduce outdoor pollution levels in their areas.

One - St Boniface RC Nursery and Primary School in Tooting, South London - had access to real-time data about local pollution levels provided by the Office of the Mayor of London.

“We were quite surprised how polluted the air is,” says headteacher Lisa Platts. “We had always assumed it was of poor quality due to the proximity to the high street, but it was worse than expected.”

This data, alongside existing concerns about traffic volumes, sparked the school into action. It signed up to the Transport for London Travel for Life accreditation programme, which encourages schoolchildren to take green, sustainable modes of transport to school. It also ran a pilot of the School Streets Initiative, which involves asking the local authority to place a temporary restriction on motorised traffic at school drop-off and pick-up times. This restriction was then made permanent in February.

Platts says it was easy to bring parents on board. “Many of our parents use public transport or walk, cycle or scooter anyway, and being on the pavements always made parents quite aware of the pollution in Tooting,” she says. “We had a huge community of parents who were willing to man barriers at pick-up and drop-off to protect children on the streets, before [our street] got cameras.”

Uphall Primary School in the London Borough of Redbridge took a similar approach to the issue, involving its pupils in the process.

Headteacher Kulvarn Atwal explains that the school’s team of pupil “Eco Warriors” looked at pollution levels and air quality within the local area.

“They found that there were places in the local area in which there were dangerous levels of air pollution, such as around busy roads,” says Atwal. “So we implemented a ban on cars around the school during the start and end of the school day.”

However, detailed data about outdoor air quality isn’t always readily available to schools, says Louise Thomas, the co-founder and CEO of Air Aware Labs, a British start-up that is widening access to air pollution data and decoding it.

“I think there’s very little awareness of the levels of pollution, both indoor and outdoor,” she explains. “Some schools might have a monitor somewhere near to them in their outdoor environment, but my suspicion is not many of them would know where it is, or if they did, how to get the data. And if they could get the data, would they know what the data actually means? There’s a huge amount to do there.”

Air Aware Labs has created a free app that anyone can use to find out this information. Thomas hopes that as access to monitoring technology becomes more widespread, it might become habitual for people to check air quality, “just like people would look up the weather forecast”.

Action group Schools’ Air Quality Monitoring for Health and Education (SAMHE) is also providing schools with indoor and outdoor air quality monitors, and has published its own recommendations to improve air quality in UK schools.

However, says Hartshorn, nationwide change can only happen with legislation. Schools can do their bit by learning to monitor air quality, decode the data and install air filters, but the real change must come from Whitehall.

“Either the government runs a public health campaign that is so compelling and so shocking that people change behaviour themselves, or we need the government to ensure that cars are cleaner, driving becomes harder and if our children want to cycle to school, that it’s actually safe for them to do so,” she says.

The government has recently announced new active travel plans that aim to get at least 60 per cent of children in England walking or cycling to school within a decade.

Backed by £4.5 billion of investment, the scheme will create thousands of safer routes and road crossings, will train children to walk and cycle safely to school, and will help schools to develop travel plans.

And with the Met Office forecasting “an increased chance of heatwaves and heat-related impacts” this summer, it looks like change can’t come soon enough.

Katie Scott is a freelance writer