Adolescents that log between six and 10 hours of sleep each night perform better in mathematics and physical education classes than those that sleep six hours or less, according to a study published in the International Journal of Clinical and Health Psychology. The researchers, after analyzing the sleep habits of 592 students aged 12 to 19 in Seville, Spain, further observed that bedtimes and wake times did not significantly influence academic outcomes; however, they did note that students that require less than 15 minutes to fall asleep tended to achieve better marks.