The teenage years are not conducive to sleep. Homework, extra curricular activities and the need to make extra money from part-time jobs all cut into a teen’s sleep schedule. In addition, teens’ circadian rhythms are working against them. Their melatonin doesn’t kick in until after 11, yet they have to get up early for school. That’s why more districts have been experimenting with later high school start times. The advocacy group Start School Later urges districts to find solutions that allow high school students to sleep in.