Sleep is important. If we don't get enough sleep, not only do we end up with bags under our eyes, our grades will suffer as well. After we've had a good night's sleep, we wake up feeling refreshed and alert. Sleep affects how we look and perform and has a major impact on the quality of our lives. Research shows that a lack of sleep makes it hard to concentrate and perform mental tasks. It has also been linked to emotional problems, like depression. And a lack of sleep also damages our ability to do our best in sport. If we don't get enough sleep, the body doesn't have time to complete all of the phases needed for muscle repair, memory consolidation and release of hormones regulating growth and appetite. Then we are less able to concentrate and make decisions. Insufficient sleep is definitely bad news - so how much sleep should we be getting? According to the experts, teenagers who want to perform well at school and in sport should be getting 8.5 to nine hours a night. The reality is that students get much less than that. One of the biggest mistakes students make is to stay up late the night before a test to cram. This is not effective. Cutting back on sleep the night before a test may mean they perform worse than they would if they'd studied less but got more sleep. Top tips for a good night's sleep Make sure your bedroom is quiet - wear earplugs if you need to. Make sure the room is dark. If your curtains aren't thick, wear eyeshades. The temperature of the room should be cool. Avoid coffee and caffeine drinks Try to get up at the same time every day. Don't have a TV in your bedroom - it's a place for sleep.