The Hechinger Report is a national nonprofit newsroom that reports on one topic: education. Sign up for our weekly newsletters to get stories like this delivered directly to your inbox.

Hotter classroom temperatures and polluted air are affecting children’s brains at school, according to a new body of education research. (AP Photo/Nick Ut)

Education researchers have traditionally focused on the obvious ingredients of teaching and learning, such as instruction, curriculum, student motivation and school funding. But now researchers are scrutinizing the physical environment that surrounds students, especially the air quality and temperature in classrooms. In the past four years, scholars have produced a growing body of research, making a persuasive case that both air pollution and heat — an increasing concern with climate change — harm student achievement.

The latest is a draft, working paper from a scholar at New York University who studied the use of air filters in one community in California and concludes that test scores rose a lot more in the schools that installed them than in nearby schools that didn’t. It’s a small study and the results seem to be influenced by one school with very large test score gains. Something other than air filters might have produced the test score improvements. The study received a lot of attention and generated controversy among statisticians, after Vox wrote about it earlier in January 2020. But it reminded me that there’s an important new body of research about air quality in classrooms that’s worth watching.

We’ve known for quite some time that pollution is bad for your health but researchers are documenting how it affects our brains. A 2016 Israel study found that high rates of pollution on the day of an exam tamped down high school test scores. The same students scored higher on different test dates with cleaner air. Boys and low-income students were the most affected. A 2019 draft, working paper of a study on university students in London also found that exposure to indoor air pollutants was associated with lower exam test scores. Again, males were more affected than females and the mental acuity problems were triggered by particulate levels that were below current guidelines at the U.S. Environmental Protection Agency. Sefi Roth, an economist at the London School of Economics, is an author of both studies.

Claudia Persico, a policy scholar at American University, has been spearheading this line of research into pollution and student achievement in this country. Three of her papers came out in 2019. One, a draft, working paper about traffic pollution, studied students from the same community and found that students who attend schools located downwind from a highway had lower test scores, more behavioral problems and more absences than students who attend upwind schools, which were more protected from toxic auto emissions. A second study found that students exposed to more air pollution in Florida had lower test scores and were more likely to get suspended from school. A third study found that children who experienced prenatal exposure to a toxic waste site had worse cognitive and behavioral outcomes than their siblings who were unaffected because of a family move or the timing of a Superfund site cleanup.

Similarly, there’s new scientific evidence for something we’ve all felt on a hot day: it’s hard to think clearly in the heat. Taking advantage of a giant data set of PSAT scores, a team of researchers examined 10 million students across the country and found that they had lower scores if they experienced hotter school days in years preceding the test, with extreme heat being particularly damaging. The study, forthcoming in American Economic Journal: Economic Policy, calculated that every Fahrenheit degree increase in the outdoor temperature over a school year reduced that year’s learning by 1 percent. (An earlier draft version was circulated by the National Bureau of Economic Research in 2018.) Given rising temperatures, those learning reductions are adding up.

Another study by Jisung Park, an economist at the University of California, Los Angeles, who was also a co-author of the PSAT study, found that just one day of ill-timed heat could have an impact on high stakes exams in New York City.  In the study, which will be published in the Journal of Human Resources, Park found that hot testing days reduced students’ performance on Regents exams, which are required for graduation in New York, and thus decreased the probability of  a student graduating from high school. For example, he found that students are 10 percent more likely to fail an exam when the temperature is 90 degrees than when it’s 72 degrees.

In the PSAT paper, Park and his colleagues make the argument that air conditioning can offset this heat problem. But they based this analysis on surveys of guidance counselors and students who answered questions about whether their classrooms felt too hot and if their schools had added air conditioners over the past decade. The researchers did not actually observe where air conditioners were running and compare test scores. It’s also possible that wealthier schools could more easily afford air conditioning and that wealthier students were more likely to score higher on the PSAT anyway. On the other hand, it’s plausible that rising heat and uneven access to air conditioning is contributing to growing achievement gaps between rich and poor that we’ve seen on several standardized tests.

Related: What 2018 PISA international rankings tell us about U.S. schools

As with the air filter study I referred to at the top of this column, it’s not yet clear that a simple remedy will make a big difference. Another unpublished study of air conditioners in Chicago public schools didn’t find an improvement in test scores in classrooms that used them, two researchers told me.

In other words, this new body of environmental research in education is still in its early stages. “We have more confidence that air pollution and heat are affecting student learning,” said Joshua Goodman, an economist at Brandeis University who is a co-author of the PSAT and heat study. “The question of what to do about it is still open. It’s not at the point where every district should be spending money on this.”

“If I were a principal or a superintendent, I wouldn’t take this research run out and spend a lot of money on air filters and air conditioners,” Goodman added. “But it’s worth thinking about if there are particular buildings where we already have a sense that there is a problem.”

Of course, teachers will tell you where the classrooms are insufferable in May, June, August and September. Pollution can be subtler. Classrooms with open windows near highways are a place to start.

The irony, of course, is that powerful air conditioners and air filtration systems use a lot of energy and contribute further to pollution and climate change. In the end, these fixes could end up doing more damage than good. Progress isn’t easy.

This story about air quality in classrooms was written by Jill Barshay and produced by The Hechinger Report, a nonprofit, independent news organization focused on inequality and innovation in education. Sign up for the Hechinger newsletter.

The Hechinger Report provides in-depth, fact-based, unbiased reporting on education that is free to all readers. But that doesn't mean it's free to produce. Our work keeps educators and the public informed about pressing issues at schools and on campuses throughout the country. We tell the whole story, even when the details are inconvenient. Help us keep doing that.

Join us today.

Letters to the Editor

At The Hechinger Report, we publish thoughtful letters from readers that contribute to the ongoing discussion about the education topics we cover. Please read our guidelines for more information. We will not consider letters that do not contain a full name and valid email address. You may submit news tips or ideas here without a full name, but not letters.

By submitting your name, you grant us permission to publish it with your letter. We will never publish your email address. You must fill out all fields to submit a letter.

Your email address will not be published. Required fields are marked *