A new research on students' sleeping habits says that more than 70% of students do not get enough sleep.

    Researchers found that primary school students get 9 hours and 10 minutes of sleep a night, junior high school students get 8 hours and 6 minutes, and senior high school students get 7 hours and 9 minutes. None of those hours are enough for each group. Not enough sleep can cause many kinds of problems in children and teenagers.

    In 2007, Shanghai Municipal Education Commission asked primary and middle schools in the city to adjust their timetables so that students could get more sleep. Two years later, a research found that students at schools that adjusted their timetables got more sleep than in 2005.

    The researchers hope that the government will take measures to make students have enough sleep. Students in other places may even less sleep than those in Shanghai.