Like many American high school students, Josh Leong used to eat breakfast while it was still dark outside. But that changed when his high school, McLean, in the American state of Virginia, changed to a later start time two years ago. The issue of school start times has become increasingly important in recent years. A growing number of sleep research studies have pointed to high schoolers' need for more sleep. The American Psychological Association, or APA, says that more than half of teens between ages 15 and 17 sleep for 7 or fewer hours per night. Teens like to stay up at night. They tend to go to bed late and wake up late in the morning. These habits are a result of biology, according to the APA. Changing the sleep schedule of teens may not work. Simply going to bed earlier does not necessarily make someone less tired in the early morning hours, says a statement on the organization's website. The American Medical Association, or AMA, has also advocated for later start times.