How installing air cleaners in classrooms can boost exam results

In 2015, Aliso Canyon experienced the worst single natural gas leak in US history. The environmental impact was equivalent to the annual emissions of 572,000 passenger cars, creating an air quality emergency. This event raised significant concerns among parents and school administrators about the potential effects on children attending nearby schools.

To address these concerns, portable air cleaners were installed in every classroom, office, and common area in schools located within five miles of the leak. In total, 1,756 air cleaners were deployed across eighteen schools. Additionally, activated carbon filters were added to the HVAC systems of these schools if they were not already present.

Impact on student performance

Michael Gilraine, Assistant Professor of Economics at NYU, conducted a study to assess the impact of these air filters on student performance. He analysed:

• Student performance in schools just inside the five-mile boundary compared to those just outside it.
• Math and English test scores over a seven-year (placebo) period before the installation of the air filters, then compared it with the results after.

Key findings

Gilraine's research revealed significant improvements in test scores:

• Math scores increased by 0.20 standard deviations.
• English scores increased by 0.18 standard deviations.

To put this into perspective, a 0.20 standard deviation gain could be equivalent to two and a half months of extra learning ⁽¹⁾. Achieving similar improvements typically requires reducing class sizes by one-third ⁽²⁾, which is much more costly.

Cost-effectiveness

The cost of achieving a 0.2σ gain through air filters was estimated at US$1,000 per class over five years, covering the device, running costs, and replacement filters. In contrast, reducing class sizes by one-third would necessitate hiring additional teachers, with average earnings of around $75,000 per year in LA, not including benefits.

For even greater cost-savings, the Blast air cleaner from Smart Air is around £600 (including running costs and filters covering a 5 year period) with benefits beyond affordability. Known for being the quietest air cleaner in its class, the Blast has a top noise level of 43dBA while churning out a whopping 950m3/hr of clean air!

This can be replicated across the country

Interestingly, tests conducted around the time of the filter installation showed no unusually high levels of pollution linked to the gas leak. This suggests that the filters improved indoor air quality by removing common pollutants found in the Valley. The educational performance improvements observed could likely be replicated in other schools across the country.

Caution and further research

While it's premature to make broad conclusions from a single study, the promising results suggest it would be worthwhile for a few cities to experiment with installing air filters in their schools. This would provide more data and help determine the true impact of cleaner air on student performance.

References

1. https://cleantechnica.com/2020/01/14/air-filters-used-in-la-schools-linked-to-higher-test-scores/
2. The Project STAR RCT in the 80s and Krueger (1999), for instance, finds that reducing class sizes by seven students (from a base of twenty-two) raises test scores by 0.2σ