Want to do well at school? Then, cut down on your lie-ins, as teenagers do not need more than seven hours of sleep a day, scientists say.
A team at the Brigham Young University in Utah found that teenagers performed better academically if they had more regular sleep patterns limited to just seven hours.
It's believed that a typical 16-year-old needs nine hours of sleep a night, but the optimum amount is just seven hours, said lead study author Eric Eide.
"We are not talking about sleep deprivation. The data simply says that seven hours is optimal at that age," Eide is quoted as saying by the Daily Mail.
The researchers said the right amount of sleep decreases with age, while the optimum amount of sleep for a ten-year-old is around nine hours, it is eight hours for 12-year-olds.
For their study, published in the Eastern Economics Journal, the researchers looked at 1,724 primary and secondary school students across the US, assessing how much sleep they got and how they scored in standardised tests. The impact of sleep on test scores depended on a number of factors, such as how educated the child's parents were.