Teenagers need to sleep more

Japanese teenagers don’t sleep nearly enough and it’s affecting their schoolwork.
Here is some recent research from Sweden;

A new Swedish study shows that adolescents who suffer from sleep disturbance or habitual short sleep duration are less likely to succeed academically compared to those who enjoy a good night’s sleep. In a new study involving more than 20,000 adolescents aged between 12 and 19, researchers demonstrated that reports of sleep disturbance and habitual short sleep duration (less than 7 hours per day) increased the risk of failure in school.
Lack of sleep increases risk of failure in school