It is recommended that elementary aged students get 10-12 hours of sleep nightly, and adolescents get eight to nine hours on a regular basis to be at their best. Monitoring electronic media exposure can help students to fall asleep more easily. In addition to limiting the amount, it is also important to turn off all sources of screen time at least an hour before bedtime.
Kids sleep patterns affected by electronic media time and media presence in the bedroom – 24 July 2013 by BioMed Central Limited
(The study, here by Teija Nuutinen1, Carola Ray1, Eva Roos)