We tend to explain test scores with the obvious things: the teacher, the curriculum, the kid, the home. One variable that almost never comes up is the air in the room. A study of 140 classrooms says it should. Across 3,109 fifth-graders, the rooms that brought in more outdoor air scored measurably better on the state math test, and the typical classroom ran at about half the fresh air the standard called for.
What the study measured
Ulla Haverinen-Shaughnessy and Richard Shaughnessy, of the University of Tulsa Indoor Air Program, monitored 140 fifth-grade classrooms across 70 elementary schools in one Southwestern U.S. district over the 2008-2009 school year, and published the results in PLOS ONE in 2015. They then matched the air data to standardized test scores for 3,109 individual students — not school averages, but actual pupils, with their family income, English proficiency, and school moves accounted for.
They worked out each room’s fresh-air rate from the carbon dioxide (CO2) that builds up when people sit in it. The average classroom brought in 3.6 liters per second per person of outdoor air (95% CI 3.2 to 4.0). The ventilation standard at the time asked for 7.1. So the typical room ran at about half. And 76% of classrooms kept their windows shut on a normal day, leaving the mechanical system to do all the work.
What they found
In the fully adjusted model, every extra liter-per-second-per-person of fresh air went with 7 more points on the math test (95% CI 1 to 12). A cooler room helped too: each 1°C drop, within the 20-25°C range they observed, went with 13 more points (95% CI 1 to 26).
+7 math points per extra liter/second of fresh air per person (95% CI 1 to 12); +13 points per 1°C cooler (Haverinen-Shaughnessy & Shaughnessy, 2015).
Across the whole observed span, that works out to an effect near 74 math points for ventilation and 67 for temperature. For scale, the state set 2,100 as “met standard” and 2,400 as “commended” — a 300-point gap. Ventilation and temperature together explained about 10% of the school-to-school difference in average math scores.
The same team’s earlier analysis of this district put it in plainer terms: for every liter-per-second-per-person of extra fresh air, up to 7.1, the share of students passing rose 2.9% in math (95% CI 0.9% to 4.8%) and 2.7% in reading (0.5% to 4.9%).
+2.9% passing math · +2.7% passing reading per extra liter/second/person of ventilation, same district (Haverinen-Shaughnessy et al., 2011).
Why fresh air would move a test score
This part is the likely mechanism, not something this study proved. When a room is under-ventilated, CO2 and other occupant-generated pollutants climb through the day. Higher CO2 has been tied in chamber studies to slower, worse decision-making, and heat adds its own drag on concentration. Children sitting six hours in a stuffy, warm room are taking the test on a tired brain.
What actually helps
The direction holds when researchers intervene, not just observe. Controlled classroom experiments in Denmark by Wargocki and Wyon found children worked school tasks about 8% faster when outdoor-air supply was roughly doubled, with no rise in errors. A California study of illness absence found a 1.6% drop in sick days per extra liter-per-second-per-person of ventilation.
Here is where the marketing goes sideways. “Air-purifying” gadgets sold for sharper focus rarely help with this, because most classroom and home stuffiness comes from too little outdoor air, and a filter can’t add outdoor air. A HEPA unit pulls particles out of what is already in the room; it does nothing about CO2, which only drops with real air exchange. Ozone-generating “purifiers” are worse: the EPA warns they release a lung irritant and are not effective air cleaners.
The useful moves are dull and cheap. Open a window when the weather and outdoor air allow. Run mechanical ventilation on its highest reasonable setting during occupied hours. Watch CO2 as your gauge — a reading that sits above 1,000 ppm means the room is under-ventilated. Keep the thermostat toward the cooler end of comfortable rather than the warmer.
A note on certainty: this is an observational, cross-sectional study. It shows an association, not proof that opening the dampers raises scores. Ventilation was estimated from CO2, not measured directly, and it covers one district, one climate, one grade. The confidence intervals are wide — the math effect runs from 1 point (trivial) to 12 (real) — so the size is uncertain even though the direction is clear. What survives those caveats: in the same students, after adjusting for income and language, the rooms with more fresh air and cooler air scored measurably higher, and controlled experiments point the same way.
Not sure how your rooms breathe? You can measure it. illumenair tests indoor air in Portland and Vancouver homes and offices — ventilation, CO2, moisture, and mold — then gives you a plain-language report and a prioritized action plan. 971-363-5626 · info@illumenair.com · illumenair.com
Sources: Haverinen-Shaughnessy U, Shaughnessy RJ. “Effects of Classroom Ventilation Rate and Temperature on Students’ Test Scores.” PLOS ONE 2015;10(8):e0136165. · Haverinen-Shaughnessy U, Moschandreas DJ, Shaughnessy RJ. “Association between substandard classroom ventilation rates and students’ academic achievement.” Indoor Air 2011;21(2):121-131. · Wargocki P, Wyon DP. “The effects of outdoor air supply rate and supply air filter condition in classrooms on the performance of schoolwork by children.” HVAC&R Research 2007;13(2):165-191. · Mendell MJ, et al. “Association of classroom ventilation with reduced illness absence.” Indoor Air 2013;23(6):515-528.