London’s low emissions linked to improvement in school tests

Academics have expressed doubt about the findings, suggesting that more evidence is needed to link the improved test scores to reduced air pollution

Research by the Grantham Research Institute on Climate Change and the Environment has found that since the Greater London low-emission zone (LEZ) was introduced in 2008, primary school students within the zone, have experienced a “meaningful improvement” in their Key Stage 2 (KS2) test scores at age 10/11.

The report authors state that this improvement is equivalent to “reducing class size by 10 students or paying teachers large financial bonuses”, and almost equivalent to “significantly increasing average teacher quality”.

The LEZ was introduced to reduce the exhaust emissions of large diesel-powered vehicles in London. It is distinct from the ultra-low emission zone (ULEZ), introduced in 2019, which applies to all vehicles.

Lead author Sefi Roth, Associate Professor of Environmental Economics in the Department of Geography and Environment at the LSE said: “Our analysis showed a statistically and economically significant improvement in test scores for students located within the LEZ compared with those in a control group.

“Importantly, we also found that the LEZ policy has larger positive effects in low-performing schools, demonstrating its potential to significantly reduce educational disparities.”

Sustainability champion Tim Smedley, author of Clearing the Air, welcomed the study. He said: “It's been known for some time that LEZs work. The UK government's Clean Air Framework in May 2017 identified Clean Air Zones as the most effective way to improve roadside air quality.

“The link between air pollution and mental health, concentration and cognitive ability have also long been known, so an uptick in school performance isn't too surprising."

“Showing that reducing pollution exposure is beneficial to children’s learning achievements is so important…” 

Professor Sir Stephen Holgate, UKRI Clean Air Champion and Special Advisor to the RCP on Air Quality, agreed. He said: “Early childhood exposure to air pollution has been linked with impaired performances in cognitive tests, inattentiveness, impaired memory development and worse academic performance.

“Showing that reducing pollution exposure is beneficial to children’s learning achievements is so important because compromised learning ability in childhood will have life-long impacts." 

However, some academics cast doubt on the claims made by the researchers. Professor Kevin McConway, Emeritus Professor of Applied Statistics at the Open University, described them as “verging on the irresponsible”. He said: “The press release uses language of cause and effect without expressing any doubt that the change in test scores was caused by the LEZ.

“I don’t believe that the analysis in the paper establishes this anywhere near firmly enough to make the claims that are made.”

Dr Gavin Stewart, a reader in interdisciplinary evidence at Newcastle University, added: “They’re making very bold claims. It seems unlikely that the effect magnitude associated with air pollution would be larger than other drivers, notably socioeconomics and educational funding.”

A Grantham Institute spokesman responded: “The paper was reviewed by two senior researchers at LSE who were not involved in the work and we are in the process of submitting it for publication in a leading economics journal.”