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School Daze

Some schools in the U.S. are opting for later start times so students can get more sleep.

By Jennie Wood

Students taking a test

Students taking a test

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Studies over the years have shown that teenagers need 9.25 hours of sleep every night to be fully alert the next day. However, most teens usually get less than seven hours per night. According to research, one reason for the lack of sleep is that biological clocks change after puberty so teenagers are more alert later at night. Therefore, teenagers have a hard time falling asleep at a bedtime that will give them that needed 9.25 hours. The lack of sleep leaves students sleepy during the school day, which can affect their academic performance. This dilemma is why some school districts across the U.S. are opting for later start times.

One of the studies that brought attention to this issue was William C. Dement and Dr. Mary Carskadon's Multiple Sleep Latency Test. Designed in 1977, the test measured sleepiness by how fast it took people to fall to sleep. It was given to teenagers at different times during the day. The test showed that teenagers were more alert at 8 p.m. than they were earlier in the day. The test also showed that teenagers were even more alert at 10 p.m.

Changes in Melatonin

Carskadon conducted another experiment centered on changes in melatonin. Based on saliva samples, Carskadon found that melatonin secretion occurred at a later time in mature adolescents, those that have gone through puberty. Therefore, it was more difficult for them to go to sleep at an earlier time. Carskadon also discovered that the melatonin secretion turned off later, which made it harder for teenagers to wake up early.

The studies of Carskadon, Dement and others have proven that around the age of 11 or 12, the biological clock in the brain adjusts to a later time. The biological clock dictates when one feels sleepy and when one is alert. It is because of this change that teenagers feel most alert at night. For a teen to get 9.25 hours of sleep and make it to school on time the next morning, they need to sleep from 10 p.m. until 7:15 a.m. Even if a teenager can get to sleep at the time when they are most alert, many high schools start by 7:15 a.m., meaning he or she has to be up before then to get to school on time. "Even without the pressure of biological changes, if we combine an early school starting time—say 7:30 a.m., which, with a modest commute, makes 6:15 a.m. a viable resting time—with our knowledge that optimal sleep time is 9.25 hours, we are asking that 16-year olds go to bed at 9 p.m. Rare is a teenager that will keep such a schedule. When biological changes are factored in, the ability even to have merely 'adequate' sleep is lost," Carskadon explains.

Adapting to Student Biological Clocks

Carskadon has urged schools to apply this research, "Given that the primary focus of education is to maximize human potential, then a new task before us is to ensure that the conditions in which learning takes place address the very biology of our learners." Therefore, some schools throughout the U.S. have adapted their start and end times with this shift in biological clocks to help students reach their academic potential.

Minneapolis and the suburb of Edina changed the start times of their high schools. In Minneapolis, the start time was moved from 7:15 a.m. - 1:45 p.m. to 8:40 a.m. - 3:20 p.m.; meanwhile in Edina, the 7:25 a.m. - 2:10 p.m. school day became 8:30 a.m.- 3:10 p.m., both having successful results.

Results of Later School Start Times

Other states, like Massachusetts and Kentucky, have also delayed some high school start times with success. These three states have seen the following positive results at high schools with later start times:

    Students eat breakfast more often
    Students appear more alert in the classroom
    Students visit the school nurse less often
    Students arrive to school on time more often
    Overall attendance increases
    Homework is completed more often and on time
    Students get better grades†
    Teenagers (16 and over) are involved in fewer car crashes‡

However, there are some drawbacks to the later start times. Here are some of the negatives that schools with later start times face:

    Students have less time for jobs after school
    The later schedule interferes with sports, arts, and other after school activities
    Families have less evening time together
    The later schedule can also cause conflicts with parents and teacher schedules
    Transportation arrangements to and from school can become more difficult

Here are a few tips for teenagers to help get the 9.25 hours of sleep that they need: Avoid stimulants, such as caffeine and nicotine, which can disturb sleep, avoid eating late, use bright lighting in the morning to help wake up, but avoid bright lights at night when winding down. Regardless of whether a high school has moved to a later start time or not, all teenagers can make adjustments, such as these, to get the sleep they need.


    †According to a Massachusetts study
    ‡According to a Kentucky Study

Source: National Sleep Foundation, U.S. Department of Education

Information Please® Database, © 2007 Pearson Education, Inc. All rights reserved.

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In 1993, Toni Morrison became the first African-American woman to win the Nobel Prize for literature.

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