Stuffy classrooms may lower test scores

Study hard. Get plenty of sleep. Eat a good breakfast. Each of these things can help students do their best on exams. Now scientists say another feature might also boost test scores: fresh air.

Students in stuffier classrooms did worse on standardized tests than did students in buildings with fresher air, two new studies found. The effect was small. But in one of the studies, it held up even after researchers considered other factors that have been linked to student achievement — such as how well they spoke English and how much their parents earned.

Scientists can gauge the quality of indoor air by measuring how much outside air cycles through a building. That air circulation is called ventilation. Opening windows can help supply fresh air. Some buildings also use fans or blowers to bring in outdoor air and push out pollutants.

One concern is carbon dioxide, or CO₂. Each time someone exhales, CO₂  is released into the air. When rooms aren’t well ventilated, the level of CO₂ in those rooms can build up. A 2012 analysis showed that college students had more trouble concentrating when indoor CO₂ levels were high. And other research has found that elementary school students with stuffier classrooms more often stayed home sick.

In a different study, researchers analyzed air quality in 100 fifth-grade classrooms. They found that in most, air quality did not meet recommended standards. That research also showed that students who got to breathe the fresher air in school performed better on their standardized tests.

These same research groups now find that better air is linked to better individual test scores too.

Ulla Haverinen-Shaughnessy and Richard Shaughnessy are married engineers who conduct research on indoor air issues at the University of Tulsa in Oklahoma. They published one of the two new studies August 28 in the journal PLOS ONE.

As part of it, they monitored CO₂ levels inside and out of 140 fifth-grade classrooms at 70 schools. All were in the Southwestern United States. The CO₂ levels helped the engineers calculate how much fresh air was flowing through each classroom. Ventilation rates in each classroom were then compared to its students’ scores on a standardized math test.

Overall, the average score for this test was 2,286 points. But kids in classrooms with the best ventilation scored about 144 points higher than students breathing the stalest indoor air. That’s enough to push a student from just meeting the average score in his or her state to now reaching a “commended” score — a higher level.

Why air quality affected test scores is unclear. Perhaps stale air gives students headaches or makes it harder for them to focus, Haverinen-Shaughnessy speculates.

The second new study was published online August 18 in Indoor Air. It was led by Mark Mendell. He works at Lawrence Berkeley National Laboratory in California. As an environmental epidemiologist there, he studies how environmental factors affect the spread of disease.

Mendell’s team used CO₂ monitors to calculate air freshness in three California school districts. In all, they looked at in 150 classrooms. These researchers also looked for a link between air quality and scores on standardized tests. Their number crunching revealed a small link, or correlation. But the effect was small. Indeed, it was so small that researchers could not rule out the possibility that the link was due to chance.

Still, the two new studies suggest “fresh air matters,” says Peggy Jenkins. An environmental scientist, she heads the indoor-air office at the California Air Resources Board, a state agency, in Sacramento.

Jenkins thinks the California data might have been muddied because the various schools were in regions with different climates. And some had air conditioning, others didn’t. Buildings don’t open windows when the A/C is running. They also limit other types of ventilation because it, too, will allow the costly, cooled air to escape.

Jenkins points out that the Southwest study could better control for other factors that might have affected test scores. If students were often out sick, for example, they might not have learned what was needed to take the test. Researchers in the California study didn’t have information about student absences. That might have made it harder to see a link between stuffy air and test scores.

The Southwest study only shows that air quality and test scores are correlated. To confirm that better air causes better performance, the researchers hope to do another kind of study. In it, schools would have to commit to improving air quality. Then researchers would test whether these actions boosted scores.

Power Words

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air quality  The degree to which air within and around buildings can affect people’s health, comfort and ability to work. Air quality can be determined by measuring temperature, humidity, amount of outside air cycling through (ventilation), and exposure to other chemicals.

carbon dioxide  A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter (including fossil fuels like oil or gas) is burned. Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food. The abbreviation for carbon dioxide is CO_2.

correlation  A mutual relationship or connection between two variables. When there is a positive correlation, an increase in one variable is associated with an increase in the other. (For instance, scientists might correlate an increase in time spent watching TV with an increase in risk of obesity.) Where there is an inverse correlation, an increase in one value is associated with a decrease in the other. (Scientists might correlate an increase in TV watching with a decrease in time spent exercising each week.) A correlation between two variables does not necessarily mean one is causing the other. 

engineer  A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

environment    The sum of all of the things that exist around some organism or the process and the condition those things create for that organism or process. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature, humidity and placement of components in some electronics system or product.

environmental engineer  A person who uses science to study and improve the natural environment.

epidemiologist  Like health detectives, these researchers figure out what causes a particular illness and how to limit its spread.

pollutant A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.

standardized test  A test that is administered and scored in the same way for all students and usually is given to large populations of students (not just to individual classes). Schools administer such tests in certain subjects regularly so that they can track how well their students are performing in those school subjects. The test may be given as a paper-and-pencil exam or on a computer.

ventilation A system that supplies a room with fresh air or processes that move air around and between different rooms.