Starting high school classes just 30 minutes later leads to marked improvement in students' moods and even their overall health, CNN reports. Teens need 8½ to 9¼ hours of sleep a night, and biological changes associated with adolescence mean they naturally fall asleep later than younger kids. In a small sample—200 high school students—starting school at 8:30 rather than 8am lowered the number of students who described themselves as "unhappy, depressed, annoyed or irritated," says a new study.
Fewer students visited the health center complaining of fatigue-related ailments after the change, and attendance improved, reports Scientific American. "If you really need nine hours, and you're only getting six and a half hours or seven hours, even that extra half-hour can make a big difference," says the study's lead author.
(More sleep stories.)