暑假適合考雅思嗎?
In years with hotter weather pupils are likely to perform less well in exams, says a major study from researchers at Harvard and other US universities.
The wide range of weather conditions in the US allows comparisons within the same year group as well as with test performances in previous years.
Mr Goodman says the findings also raise bigger questions about whether climate change and global warming will have implications for school achievement.
There is a "significant" link between higher temperatures and lower school achievement, say economic researchers.
An analysis of test scores of 10 million US secondary school students over 13 years shows hot weather has a negative impact on results.
The study also asks whether heat plays a part in the huge regional differences in achievement within the US.
The study says a practical response could be to use more air conditioning.
Students taking exams in a summer heat wave might have always complained that they were hampered by the sweltering weather.