From the New York Times:
Canadian researchers have found compelling evidence that closing schools is an effective way to control flu epidemics.
Scientists at McMaster University in Ontario and elsewhere compared patterns of flu transmission with weather and school calendars in Alberta from April to December 2009. The study, published in Annals of Internal Medicine, found that transmission rates were linked to weather, but even more strongly to the closing of schools in the spring and their reopening in the fall.
“The effect of school closings was huge,” said David J. D. Earn, lead author of the study and a professor of mathematics at McMaster. “This is important because school closings, unlike weather, is something we can control.”