Weekend sleep after early and later school start times confirmed a model-predicted failure to catch up sleep missed on weekdays.

"Declarations Ethical approvalThis article does not contain any studies with human participants or animals performed by the author. Consent to participateIndividual data were not used in the present study. For the present analysis, only group-averaged values of sleep times were taken from the previously published papers. These collected mean values were included in one of supplementary files (Appendix A), and all these previously published papers were cited in this Appendix A. Each of these previously published papers contains the necessary information on compliance of those studies with ethical standards. Consent for publicationN/A Conflict of interestThe author declares no competing interests. Conflict of interest The author declares no competing interests."