Researchers have found a significant link between hot weather and poor exam results.
The findings come ahead of the Leaving and Junior Cert exams which begin next Wednesday.
Academics from Harvard, UCLA and Georgia State examined test scores of 10 million US secondary students over 13 years.
They found that when temperatures go up, school performance goes down.
The study, published by the US National Bureau of Economic Research, found that students were more likely to have lower scores in years with higher temperatures and better results in cooler years.
It said low-income and minority students were impacted by heat more than others - while air conditioning in schools all but completely eliminated the impact of heat.
File photo of Leaving Cert exams beginning in 2014 | Image: Laura Hutton/RollingNews.ie
The authors write: "We show that only school-day exposure to higher temperatures affects test scores; hot summers and weekends have little impact on achievement and controlling for such exposure does not shrink the magnitude of impact of hot school days.
"This suggests that heat’s disruption of instruction or homework time is responsible for the observed drop in test scores."
The drop in performance is significant, the research showed.
On average, student achievement fell by the equivalent of 1% of a year's worth of learning for each additional degree Fahrenheit in temperature during the year preceding the exam.
The research said a practical response could be to use more air conditioning.