This PDF file includes:

• Table S1. Demographics of students in each of the high schools included in the study.
• Fig. S1. Probability of a light measurement (among all individuals recorded) being below a threshold (X in legend) throughout the day.
• Fig. S2. Probability distribution of light measurements across all watch data from Seattle high school students in 2016 and 2017.
• Fig. S3. Representative actogram of a student in which the Actiwatch algorithm for sleep offset detection missed a sleep offset (white arrow).

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