[1]Surveys find that half of American teenagers are missing an average of up to 1.5 hours of sleep every school night.
[2]Surveys of American teenagers find that about half of them do not get enough sleep on school nights. They get an average of sixty to ninety minutes less than experts say they need.
[3]Experts say teens are biologically programmed to go to sleep later and wake up later than other age groups. Yet many schools start classes as early as seven in the morning.
[4]As a result，many students go to class feeling like sixteenyearold Danny. He is an active teen—except in the morning.
[5]DANNY：“Getting up in the morning is pretty terrible. I'm just very out of it and tired. And through first and second period I can barely stay awake.”
[6]Michael Breus is a clinical psychologist with a specialty in sleep disorders.
[7]Teens，he says，need to sleep eight to nine hours or even nine to ten hours a night. He says sleepy teens can experience a form of depression that could have big effects on their general wellbeing.It can affect not just their ability in the classroom but also on the sports field and on the road.
[8]So what can schools do about sleep students? The psychologist says one thing they can do is to ________ in the morning.
[9]Eric Peterson is the head of St.George's School in the northeastern state of Rhode Island. He wanted to see if a thirtyminute delay would make a difference. It did.
[10]He says visits to the health center by tired students decreased by half. Late arrivals to first period fell by a third. And students reported that they were less sleepy during the day.
[11]Eric Peterson knows that changing start time is easier at a small，private boarding school like his. But he is hopeful that other schools will find a way.
[12]Patricia Moss，an assistant dean at St. George's School, says students were not the only ones reporting better results.
[13]PATRICIA MOSS：“I can say that，almost all the teachers noticed immediately much more alertness in class，definitely more positive mood. Kids were happier to be there at eightthirty than they were at eight.”
20．What time may be the most suitable for school to start classes in the morning? (no more than 5 words)
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21．What does the text mainly talk about? (no more than 15 words)x k b 1 . c o m
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22．For what purpose does the writer mention Danny in the passage? (no more than 15 words)
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23．Fill in the blank in Paragraph 8 with proper words.(no more than 3 words)
The psychologist says one thing they can do is to ________________ in the morning.
24．What does the word “it”(Line 2, Paragraph 5) probably refer to? (no more than 5 words)
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