Start school later movement
In the United States, the start school later movement is an interdisciplinary effort by health professionals, sleep researchers, educators, community advocates, parents, students, and other concerned citizens working for school hours that give students an opportunity to get enough sleep at optimal times. It bases its claims on a growing body of evidence that starting middle and high schools too early in the morning is unhealthy, counterproductive, and incompatible with adolescent sleep needs and patterns. During the second half of the 20th century, many public schools in the United States began shifting instructional time earlier than the more conventional bell time, thoughtout 9 a.m. Today it is common for American schools to begin the instructional day in the 7 a.m. hour and end about seven hours later, around 2 p.m. Most sleep research suggests that morning classes should begin no earlier than 8:30 a.m. for middle and high school students.