People spend almost a third of their lives doing one thing: sleeping. Every year，there is ad for people around the world to celebrate the importance of good and healthy sleep –World Sleep Day.
Sleep is like food for the brain (大脑). A good amount of sleep helps the body and brain grow and .
People of different a need different amounts of sleep. According to the National Sleep Foundation in the US, adults (成年人) need seven to nine hours of sleep every night. For students aged 10 to 17, a healthy amount is about eight to nine per night.
H ，many students don't get enough sleep because of early school start times and too much homework. The China Youth and Children Research Center（中国青少年研究中心)reported that about 80 percent of middle school students don't get e sleep.
A lack(缺乏) of sleep can greatly affect(影响) a person's life. Students w don't get enough sleep may get poor grades. They can't pay a in class or do well in sports.
To solve this problem, scientists advise that students should have I schoolwork and more time to sleep，such as taking a 20-minute nap(午睡) during the day. Good sleep habits are also h . For example, t to go to sleep and wake up at the same time every day, even on weekends and during holidays.
