Okay, teens, here’s a question: How many hours of sleep are you supposed to get every night? If you said “nine,” you get a gold star. 

That’s because most teens and their parents have no idea that nine hours of sleep a night for young people is crucial. They also have no clue that over half of middle school students and high-schoolers are chronically sleep-deprived. 
And that’s a big deal. According to the Mayo Clinic, sleep promotes normal cell growth and boosts the immune system. Our brains also consolidate information when we sleep. Which means, skimping on shut-eye lowers test scores and makes it hard to concentrate for more than short periods of time. In fact, psychologist Dr. Jane Ansell says that the symptoms of sleep deprivation are so similar to ADD that a lot of kids end up getting prescriptions for Ritalin and Adderall when what they really need is a solid sleep schedule. 
So what’s making teens so tired? Smartphones and computer games. Oxford University neuroscientist Dr. Russell Foster says that bright screens mimic daylight, which stimulates their brain to wake up and stay alert. So even after kids stop tweeting, texting and X-Boxing, the residual energy boost from bright electronic devices can still keep them from falling asleep for hours. 
The take-home message is clear: If you want to feel better and get better grades, turn off anything with a screen two hours before bed and turn in at least nine hours before your alarm’s set to go off.