High school students suffer from mental health challenges and poorer academic performance resulting from sleep disturbances. Unfortunately, approaches to this problem sometimes focus on increasing sleep duration by going to bed early; a strategy with limited success because teens experience a phase delay in bedtimes. There is a need for approaches that leverage behavioural sleep science and are accessible, scalable, and easily disseminated to students. DOZE (Delivering Online Zzz's with Empirical Support) is a self-management app that is grounded in sleep and circadian basic science. Although initial testing supports it as a feasible and acceptable app in a research context, it has not been tested as a strategy to use in schools. The present study tested DOZE in private high schools in Canada. Two-hundred and twenty-three students downloaded the app and completed daily sleep diaries over 4 weeks. Students reported a more regularised routine for bedtime, M = -0.43 h, p < 0.001, 95% CI [-0.65, -0.21], and rise time, M = -0.61 h, p < 0.001, 95% CI [-0.84, -0.38], in addition to a higher total sleep time, M = 0.18 h, p < 0.008, 95% CI [0.05, 0.31]. Students also rated DOZE to be highly acceptable. The evidence suggests that students find DOZE to be acceptable and engagement in this nonclinical population was reasonably high under minimal researcher supervision. This makes DOZE an attractive option and a step towards broad-based sleep health services. High powered replications with control groups are needed to increase empirical rigour.