Getting enough good sleep is critical for adolescents’ health, education, and overall well-being, but data from the 2015 Youth Risk Behavior Surveillance Survey suggest that only one in four high school students (27 percent) receives more than eight hours of sleep per night. However, sleep scientists recommend that adolescents receive closer to nine hours of sleep for optimal functioning. School start times likely influence the amount of sleep that adolescents get, and policies should account for this link as early as middle school.
Across the country, school districts are heeding calls from the American Academy of Pediatrics, the Centers for Disease Control and Prevention, and other organizations to address insufficient sleep by delaying school start times, particularly at the high school level. However, as changes to start times can be costly for school districts—which may need to purchase new transportation infrastructure and take on other costs—recent shifts have led to tradeoffs between high schools and middle schools. For example, to prioritize later start times for high schools, some districts either opt against a delayed start for middle school students or have them start school even earlier in the morning. New research, recently published by Child Trends in the Journal of School Health, suggests that such policy choices may be detrimental for middle school students’ sleep.
Although advocates have long included middle schools in discussions of later school start times, most published research until recently focused on outcomes for high school students. That research consistently shows that later school start times are linked to longer sleep durations and decreased daytime sleepiness, among other outcomes. School districts’ focus on the high school level is perhaps reflective of the relative scarcity of evidence for middle schools.
As part of Child Trends’ work to evaluate one school district’s efforts to change school start times, we expanded the evidence base demonstrating that later start times are also linked to better sleep outcomes for middle school students. The analysis compared two types of schools in the same district: those that served only seventh- and eighth-grade students (middle schools), and schools that served those grade levels alongside ninth- through twelfth-graders (secondary schools). At the time of analysis, middle schools started approximately 37 minutes later than secondary schools (8:00 a.m. vs. 7:23 a.m.).
Students in each type of school were asked to respond to an online survey about their sleep and health outcomes. We used statistical weighting to better relate our findings to the differences in school start times, rather than to other characteristics (e.g., gender, race, age, or socioeconomic status) that may also contribute to differences in outcomes.
Although seventh- and eighth-grade students at later-starting schools had bedtimes approximately 15 minutes later, they received, on average, 17 more minutes of sleep per night than students in earlier-starting schools. These extra minutes of sleep add up over time—17 minutes a night leads to nearly 51 extra hours of sleep in a year. Given the known linkages between sleep, academic achievement, mental health, and physical health, such gains in sleep could have significant positive implications for these students. More research is needed, however, to really understand these long-term outcomes.
Still, even the youth in the later-starting school did not generally reach the optimal sleep duration of nine hours. Assuming a linear relationship between time delayed and minutes of sleep duration increased, our findings suggest that schools would need to start at 9:15 a.m. for students to reach nine hours—which may not be feasible for all school systems. Still, our research findings are clear: Middle school students should not be left out of the conversation around school start times.