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Moving the needle on student achievement is heartbreakingly difficult. A highly successful educational intervention, one that districts might spend thousands of dollars per student implementing, might yield an effect size the equivalent of weeks of learning. Unfortunately, most interventions fare even worse, often showing little to no measurable impact despite substantial investments.

As education leaders, we cannot afford to limit our search for solutions to what we conventionally think of as “education interventions.” What if one of our most powerful tools for improving student outcomes has been overlooked because it doesn’t fit neatly into our current frameworks?

Early evidence that air filters could improve education outcomes started to emerge years before the COVID-19 pandemic and came from a surprising source: a natural gas leak in Aliso Canyon, California. In late 2015 the gas company, facing public pressure, installed commercial-grade air purifiers in every classroom within a five-mile radius. Michael Gilraine, an economist studying the incident, recognized a rare opportunity: Schools just inside the five-mile boundary received air filters, while demographically similar schools just outside the artificial boundary did not.

Gilraine found that students in schools with air filters saw their test scores jump: Math scores increased by about three months of learning, and English scores were close behind. The gains persisted and even grew over time. To put this effect size into context, students in the most prominent class-size study, the Tennessee STAR experiment — who were randomly placed in much smaller classes averaging 15 students instead of 22 — experienced roughly similar gains.

That intervention cost about $7,000 per student in today’s dollars. The Aliso Canyon air purifiers, electricity costs, and replacement filters combined cost about $1000 per classroomapproximately $30 per student, less than 1% of what Tennessee spent to reduce class sizes by a third. With recent innovations in air purifiers, annual costs per classroom could be considerably less.

If these effect sizes replicate — and further research is needed — air cleaning would significantly outperform the highest-regarded interventions in the U.S. education world for its cost, including the Perry Preschool study, high-dosage tutoring, and Head Start.

The evidence base for the education benefits of portable air cleaners – on top of the health benefits – is growing:

Air quality improvements appear to create cascading benefits across multiple systems: First, there are direct cognitive gains. Fine particulate matter that students and staff inhale doesn’t just irritate lungs, it crosses into the bloodstream, triggers systemic inflammation and can even breach the blood-brain barrier. Breathing cleaner air helps you think faster, remember more and make fewer errors.

Second, there are direct health improvements, which in turn affect both attendance and performance. Reducing respiratory infections, allergies and asthma triggers keeps students and staff healthier and in school. Fewer sick days means more instructional time, less reliance on substitutes and better instructional continuity. And fewer infections mean fewer sick days for parents, too. At a time when measles cases are on the rise nationally, tuberculosis is at its highest rates in decades in multiple states and studies are showing the H5N1 influenza virus is airborne, this is a particularly critical moment to make sure our students can breathe safe air.

Third, this intervention helps address inherent inequalities in our education systems. Schools serving low-income communities are more likely to be near highways, industrial facilities and other sources of air pollution that are known to negatively impact students. These students are also more likely to learn in older buildings with poor ventilation and decaying materials whose dust, often toxic, ends up in students’ lungs. Cleaning the air is likely to benefit all students, but especially those who are worst off economically.

Thankfully the administrative burden, which often makes or breaks even highly promising interventions, is minimal. Reducing class sizes requires hiring more teachers, building more classrooms and restructuring schedules. High-dosage tutoring entails recruiting, training, scheduling and coordination. Air purifiers? Order them online, plug them in, and quickly change filters once a year – no need for expensive retrofits.

We cannot afford to ignore air quality in education. Many school systems recognized this during the pandemic and purchased new equipment, but some have turned off or unplugged their devices, perhaps thinking that they were only necessary during the height of COVID-19 transmission to help keep schools open. As we begin the new school year, let’s reconnect these devices and install new filters, often as little as $50 to $100 a classroom.

For school systems that don’t yet have portable air cleaners, consider first piloting and then rolling out system-wide. These districts should install devices in every classroom and staff room, aiming for a Clean Air Delivery Rate (CADR) of at least 30 cubic feet per minute per student and quieter than 50 decibels. Schools should monitor not just test scores but also absenteeism, nurse visits and teacher satisfaction.

Philanthropy can add air cleaning interventions to its portfolios alongside more traditional education grantmaking. They can create programs that provide devices to under-resourced schools, fund larger trials to further evaluate the promising findings to date, underwrite R&D for even more effective and quiet air purifiers for classrooms and develop bulk purchasing agreements to reduce costs.

Advocates and activists can build coalitions for indoor air quality standards in schools and funding for air quality programs. Researchers can advance large-scale randomized controlled trials examining student, teacher and even parent outcomes across grade levels.

We’re living through a paradigm shift in our understanding of indoor air quality which has handed education an unexpected gift: a simple, affordable, and powerful tool for improving education. We’d be foolish not to use it.

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