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    We know many students don't have enough(足够的) sleep. Many students say theygo to bed early. They stay up late because they have tolots of homework and they like watching TV and playing computer games at . A survey（调查）shows that 1/4 students don't get eight sleep every night. They often feel  and want to sleep in class. In Scotland, some schools start new subject, Sleep Class. The teachers teach the studentsto sleep well. Many students like this subject. They think it's good for their healththeir study. A 15-year-old boy says, "Now I go to bed10:00 every night. The next day, I usually get uptime and then play sports for an hour. I feel very great."