In the United States, and in many other countries, sleep deprivation is common among students. School-aged children should be getting between 8.5 and 9.25 hours of sleep[12] but many do not. A National Sleep Foundation survey found that college/university-aged students get an average of 6.8 hours of sleep each night.[13] Sleep deprivation is common in college freshmen as they adjust to the stress and social activities of college life. A study performed by the Department of Psychology at the National Chung Cheng University in Taiwan concluded that freshmen received the shortest amount of sleep during the week.[14]. Students get more sleep each night in the summer than during the school year,[citation needed] and one in four U.S. high school students admit to falling asleep in class at least once a week.[15]. Research has indicated that teenage children have a variation in their circadian cycle that delays sleep past the normal time for adults. Since school schedules are based around the adult workday, it is not surprising that students have difficulty obtaining adequate sleep.[citation needed] In 1997 the University of Minnesota did research that compared students who went to school at 7:15 a.m. and those who went to school at 8:40 a.m. They found that students who went to school at 8:40 got higher grades and more sleep on the weekdays.[16]
Source: http://en.wikipedia.org/wiki/Sleep_deprivation