The real reasons later school start times are effective

Two researchers explain how tardiness and discipline problems are linked to start times in high schools

In the U.S., 90 percent of high school students start their school day between 7:30 a.m. and 8:45 a.m. But is that the wisest approach? More recently, later start times have been advocated because adolescents have sleep-wake cycles that are delayed by puberty. For these students, in fact, peak performance has been shown to occur later in the day. Other studies show that two-thirds of adolescents on average get up to two hours less sleep than they need for optimal functioning. Maybe there’s a good reason many teens aren’t morning people.

We recently conducted a new study that used a longitudinal approach to measure the effect of delayed high school start times on students’ sleep, achievement and health — and whether changes persist. Our results suggest that delaying high school start times can robustly and persistently improve two variables that affect students, teachers, and administrators alike — tardiness and disciplinary problems in the classroom.

These results are consistent with many past studies that examined start time changes, adding further support to recommendations by the American Academy of Pediatricians that high schools should not start the school day until 8:30 a.m. or later.

In our research, we tracked sleep, mood, health, attendance, tardiness, problem behaviors, and academics, in a high school that delayed start time by 45 minutes.

Our participants included high school students in the Glens Falls, N.Y. school district. We collected data from school records, from academic testing results, and from the students directly. In May 2012, before the change was instituted, we collected baseline data, and then collected data in November 2012 and again in May 2013, after the start time was delayed by 45 minutes (7:45 am to 8:30 am). Reports from school records regarding attendance, tardiness, disciplinary violations and academic performance were collected for two years prior (2010-2012) and two years after the start time change (2012-2014).

When start time was delayed, school records showed dramatic and persistent reductions in tardiness and disciplinary incidents.

So what happened? When the start time was delayed, virtually all students slept in later — consistent with what we would expect, given that students this age strongly prefer a later start time. The school records showed dramatic and persistent reductions in tardiness and disciplinary incidents. Other variables in which we were interested, however, failed to show improvements. For example, students showed no persistent increase in total sleep time in this study. And no changes — for better or worse — were detected in the areas of physical or mental health; no changes to exam grades or standardized test scores were detected, either.

Why did we not see improvements to these areas? We believe this is because, although students initially slept longer (by about 20 minutes at the first follow-up), these gains did not persist longitudinally. Therefore, the students experienced a delay in bedtimes and wake times, but no overall increase in the amount of time they reported sleeping. It’s difficult to imagine that any changes to the broader well-being of students could occur unless students slept longer, as well as later.

Despite the fact that changes did not occur across all variables, we were encouraged to see the improvements to tardiness and disciplinary incidents: improvements in these domains can help every student in the classroom. Furthermore, because schools are required to execute many expensive and time-consuming follow-up actions on behalf of late and aggressive students, anything that reduces these issues can be of tremendous worth to school districts.

In short, we believe that longer sleep times, coupled with delayed timing, may both be necessary to realize improvements to mood, health, and academic performance. A start time delay is a first step, and may, all on its own, effect changes in behavior and on-time arrival. But school start time delays are not like Jack’s magic beans in the old fairy tale: one can’t scatter the seeds and then watch the bean plant grow towards the clouds, all on its own. Start time changes can provide the impetus for many students to sleep later, but our communities as a whole must provide the encouragement and the examples to our students in order to allow sleep to take its place as a critical element of physical, mental, and cognitive health. A comprehensive effort to educate and persuade constituents of the benefits that can occur when sleep is improved may be needed to implement delays in school start times and to maximize the benefits that can follow.

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