Make Schools Cool

Last week Europe burned. In the UK, the highest temperature on record was exceeded in more than 20 locations. Most schools were still in session. With no air conditioning to speak of, students and teachers were forced to learn and teach in temperatures above 35 degrees Celsius (95 degrees Fahrenheit).

For the UK—which is not known for its hot weather, although heat waves are becoming an increasingly frequent feature of British summers—this was an unusual event. But in many developing countries, temperatures exceed 30 degrees Celsius (86 degrees Fahrenheit)  on a regular basis. In Africa and South Asia the average person has, in recent years, experienced extreme heat (above 46 degrees Celsius or 114 degrees Fahrenheit) for five days per year, a 30 percent rise compared with 1980-1984. Most schools on these continents operate without air conditioning, and often with poor insulation and limited natural ventilation.

Conditions like these are, of course, uncomfortable for both children and teachers. But a growing body of evidence suggests that high temperatures could have a negative impact on children’s education outcomes and could even wipe out the impact of median-effect education interventions. The top priority must be a concerted global effort to tackle climate change. But in the meantime, ways to mitigate the impact of high temperatures on children’s wellbeing and education—i.e. climate adaptation measures—should be urgently explored.

In this blog we examine the evidence on the impact of hot schools and discuss the options available to education policy makers.

Figure 1. Temperatures are rising

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Hot weather has a negative impact on education outcomes

Prolonged exposure to heat, during the school year and exam-time can lead to delayed educational achievement. While evidence from developing countries is limited, there are two main ways high temperatures have a negative impact on children’s education.

The first is persistent hot weather—i.e. a high number of hot days each year, every year—which affects long term learning outcomes, either through a physiological mechanism where high temperatures cause cognitive impairment (e.g. loss of concentration) or through income shocks which reduce education investments. The second is hot weather that occurs during high stakes exams, which affects student performance. Other less-evidenced channels that may affect children’s outcomes include teacher absenteeism due to hot weather and increased prevalence of disease.

Children learn less when schools are persistently hot

Children in hot countries tend to perform worse at school. Across countries, a 1 degree Fahrenheit increase in average annual temperature is associated with 0.02 standard deviation lower score in the 2012 PISA maths test (Park et al, (2020), though there are many factors other than hot weather also affecting this lower performance. Garg et al. (2020) examine in detail how hot weather affects children’s education performance in India, using the number of hot days (above 29 degrees Celsius or 84 degrees Fahrenheit) each year. On average there are 50 days per year in India with a mean temperature exceeding 29 degrees Celsius (84 degrees Fahrenheit), compared with less than 10 days in the US. They find that 10 extra hot days reduces maths and reading scores on ASER and Young Lives tests by at least 0.03 and 0.02 standard deviations respectively across the whole ability spectrum.

If 10 days of hot weather occurs during the growing season —the period of the year when temperatures are generally right for crops to grow—the impact is even greater, equivalent to around 0.35 years of schooling. This may be because of the loss of agricultural income caused by extreme weather, which reduces parents’ investments in children’s education. With the number of hot days in India expected to double to 100 by the end of the century, Garg et al. estimate that learning loss due to hot weather will be equivalent to more than two years learning over a child’s 12 years of schooling and a decrease in wages of nearly 20 percent.  These effects are large: 10 extra hot days during a growing season could zero out any gains made from a median educational intervention (McEwan (2015)).

In a rich country context, Park et al, (2020) provide causal evidence on the link between hot weather and learning outcomes in the US. They show that a 1 degree Fahrenheit higher annual temperature reduces test score performance by around one percent of an average student’s annual learning gain. However, extreme temperatures have a stronger negative impact: each additional day above 32 degrees Celsius (90 degrees Fahrenheit) reduces learning by 0.6 percent of average annual gain. If students are persistently exposed to hot weather over multiple years, the cumulative effect is larger—reducing their learning by around two percent of average annual gain. They find that hot weather disproportionately affects minority students and accounts for up to 13 percent of the U.S. racial achievement gap. This is both because Black and Hispanic students live in hotter parts of the country and because extreme heat damages the achievement of minority students more than white students.

Children do worse in exams on hot days

Taking an exam on a hot day lowers children's scores. In China, a 3.29 degree Celsius increase from the average temperature (23.1 degrees Celsius or 73.6 degrees Fahrenheit) during the national college entrance exam period decreased students’ test scores by about 1.12 percent (Graff et al.(2020)). Graff et al. also examine the relationship between hot weather during exams and access to top tier universities. The findings reveal that similarly, a 3.29 degree Celsius increase in temperatures above 20 degrees Celsius (68 degrees Fahrenheit), decreased the probability to get into the best universities by almost 2 percent. When access to air conditioning is not harmonised across regions, this creates inequalities among candidates.

In India, Garg et al. (2020) find a 1 degree Celsius increase in temperature above 23 degrees Celsius (73 degrees Fahrenheit) on exam days reduces test performance in maths by 0.17 standard deviations. They found no relationship between higher temperatures and reading, perhaps because the part of the brain responsible for maths problems is more temperature-sensitive than the portions responsible for reading functions.

The evidence of heat exposure on high stake exams goes beyond developing countries. Sampling the United States largest school district in New York revealed that hot exam days (90F and above) reduced performance on a particular subject by 10.9% on average (Jinsung Park, (2018)).

Education policymakers should find ways to make schools cool

Since 1980, each decade has been warmer than the previous one and the hottest years on record have occurred since 2015. More people are exposed to heat stress, and the ratio is higher in Africa and parts of Asia.

What needs to happen, of course, is a serious global effort to tackle climate change. But in the meantime—as rising temperatures are harming children’s education and life outcomes—education policymakers around the world need solutions to mitigate the cumulative effect of long heat exposure on educational achievement. Currently, there are few affordable policy options for their consideration. 

The optimal policy option would be to improve ventilation and air conditioning in classrooms and exam centres to keep them at a comfortable temperature of around 22 degrees Celsius (72 degrees Fahrenheit). It’s conceivable that rich countries, like the UK, will increasingly invest in air conditioning in schools, although of course air conditioning uses a lot of energy. In developing countries, where temperatures tend to be higher, investing in air conditioning would constitute a substantial stretch in their budget allocation and will almost certainly be unaffordable at a wide scale.

A second and more reasonable policy option is to move the exam period to cooler months. High stake leaving exams usually occur during summer and moving it even a couple months earlier to March or April could make it easier on kids. A related option is to consider heat-adjusted-grading. Jinsung Park (2018) finds that teachers in New York tend to be more flexible when grading exams that were taken on a very hot day. This will require more research to adjust for scores based on the conditions (temperature) in which kids took the exam. Moving exams would help mitigate exam-related heat stress but would not mitigate long term effects on learning caused by high temperatures.

Other low-cost ways to keep children and teachers cool include changing school hours to avoid the hottest part of the day, planting more trees to provide shady areas to learn, ensuring a regular supply of drinking water and adopting school uniforms more suitable for hot weather. More research on the best, affordable ways to keep children cool in school should be undertaken urgently.

The time to act is now

Extreme heat is becoming an ever-common part of life in poor and rich countries and all these policy options require advanced planning.  Education policymakers should not wait for the next period of extreme temperature to consider how to keep schools safe for children and staff. The time to act is now, before climate change further damages the life chances of current and future generations.

Thanks to Aisha Ali and Maya Verber.