As the school year goes on and the weather gets warmer, are your test scores dropping? According to recent studies, scientists have found that there is a significant link between higher temperatures and lower test scores.

The recent study has been the work of various renowned colleges including Harvard University, the University of California at Los Angeles, and Georgia State. The paper, called “Heat and Learning,” was published by the National Bureau of Economic Research, a nonprofit research organization. For the past thirteen years, the researchers have been following the test scores of over ten million students all across the nation.

From analyzing PSAT scores from 2001-2014, scientists found that once classroom temperatures rose above 60.8-68 degrees Fahrenheit, test scores began to drop, especially once temperatures reached 80 degrees Fahrenheit. Also, for every half degree increase per year, there was a one percent fall in learning. This finding appeared all across the country – from the colder Northern states to the sweltering South – hot temperatures affect test scores.

As temperatures increase, students find it easier to get “distracted, agitated and find it harder to focus,” according to Joshua Goodman, a professor at Harvard Kennedy School of Government. Instead of being focused on schoolwork, students instead become focused on maintaining a lower body temperature. Working in the heat makes students more tired as well.

The effect on lower-income families was more prominent in the study as well. The study provided a simple explanation to this fact – students in more affluent areas went to better schools. Schools that had more money could afford air conditioning in their buildings, no matter how much more the temperature increased.

The fix to preventing the decrease in test scores is simple – schools need to be willing to spend the money on air conditioning. While the statistics may appear small per year, according to the study, if temperatures continue to rise this quickly then students in warmer classrooms could have significantly lower wages in the future.