By Robbie Webber
A study from the National Bureau of Economic Research extends our knowledge of the effects of attending school near major roadways. Previous studies have found short-term effects on test scores, behavior, and school absences on days of poor air quality, but this new research shows that long-term school performance and test scores can be affected by attending school downwind of highways.
The study involved children in Florida who changed schools due to moving from middle school to high school or elementary to middle school without changing their residence. This avoided the self-selection of families who chose to move away from or not have their children attend schools near heavily-trafficked roads when their overall household circumstances changed.
Children who had been upwind of, or not close to, a highway and moved to a school that was downwind and in close proximity to a large roadway showed a significant change in overall school performance. And the effects are long-lasting.
We show that children who move to a school downwind of a major highway have lower test scores and a higher likelihood of behavioral incidents and missing school than when those same children attended schools with similar characteristics that were not downwind of a major highway. The effects are larger for more heavily-trafficked roads, and the effects appear to last even after the child moves away from a downwind school. This suggests that once damage from pollution is done, even during middle childhood, it might persist, potentially affecting outcomes far into the future.
The authors compared the differences in performance attributed to proximity to roadways to the changes that can be attributed to quality of teachers or a change in class size.
The magnitude of these effects are substantively important, especially when one considers that 6.4 million children (or about 12.6 percent of public and secondary school students) attend school within 250 meters of a major roadway. To put this in context, [previous researchers found] that a one standard deviation improvement in teacher quality increased test scores by 0.1 standard deviations. This suggests that removing exposure to local highway pollution would increase test scores as much as increasing teacher quality by 40 percent of a standard deviation. Our findings are about one fifth of the magnitude of the Tennessee STAR experiment, which found that reducing class sizes from 22 to 15 students increased test scores by about 0.2 standard deviations.
School districts often buy land and build schools near large roads both because the land is inexpensive and in order to make transportation easier for parents. However, these reasons may backfire in a number of ways. Traffic created by parents driving their children to school may result in the need for local transportation agencies to widen roads or add signals where none were needed previously, as noted in a 2012 SSTI report on school siting for the Kansas Department of Transportation. Large roads also make it harder for children and parents to access the school without driving. And with this study, we can add concerns about student performance when considering school siting decisions.
Robbie Webber is a Senior Associate at SSTI.