The Impact of School Start Times on Adolescent Health and Academic Performance

“Inherently, the majority of kids with a later start will get more sleep, which is beneficial to grades as well as being safer.” ⁽⁶⁶⁴⁾—Philip Fuller, M.D., Medical Director, Mary Washington Hospital Sleep and Wake Disorders Center.

A 2008 study of 42 Brazilian teenagers (ages 14-19) in 3 high school classes found the students maintained irregular sleep schedules while vacationing, suggesting that early start times are not the “sole cause” of adolescent sleep irregularity. ⁽³³⁾ The survey data, gathered from one week during the school year and one week during the vacation period, showed that while on vacation, the teens’ average sleep on weekdays (9 h. 37 min.) was longer than on weekends (8 h. 57 min.), ⁽³³⁾ whereas during the school year, the teens slept longer on weekends (8 h. 37 min.) than on weekdays (8 h. 9 min.); i.e., the students’ sleep schedules were “inverted[.]” ⁽³³⁾

“It is probable that the weekend ceased to be the period when they compensated for sleep missed during the week; perhaps this has become the period when they develop stimulant social activities such as going to parties, navigating on the internet, or watching TV until late, a common practice among adolescents.” ⁽³³⁾

Although the researchers recognize that “morning school schedules are the chief cause for adolescents’ partial sleep deprivation and sleep schedule irregularities[,]” they comment that delaying school schedules to allow for additional sleep may prove an ineffective intervention if students simply stay up later to play electronic games, etc. ⁽³³⁾ While postponing bedtimes undoubtedly reduces the time available for weekday sleep, the evidence thus far rather clearly establishes that the great majority of students choose rest over recreation when schools delay the morning bell. As explained by neurologist Helene Emsellem, Medical Director of the Center for Sleep and Wake Disorder in Chevy Chase, Maryland:

“Contrary to what you might think, teens whose schools have later start times do use the extra time for sleep; they don’t stay up later, but go to sleep at the same time they always have and sleep later in the morning.” ⁽⁴³⁾

In evaluating the likelihood the Brazilian researchers’ concerns may be realized, notwithstanding any holiday sleep irregularity (cf. ns. 6, 665 [without interference from a school schedule, U.S. adolescents’ weeknight sleep matched their weekend sleep]), first, as previously observed (see, § I, supra), restricted sleep among adolescents is confined almost exclusively to school nights, rather than weekend or summer nights, ^{(21, 22, 26, 28, 29, 30, 55, 101, 102, 109, 110)} with older students losing nearly 3 hours of sleep each night after the start of school. ^{(2, 6, 65, 107,} see also, Mindell & Owens, Clinical Guide to Pediatric Sleep: Diagnosis and Management of Sleep Problems (Lippincott Williams & Wilkins, 2nd ed. 2010) p. 258.) “The cause of this decline in sleep duration is shown in the difference between sleep on education/work days and free days.” ⁽⁶⁵⁾

Second, as authority for the proposition that children may postpone bedtimes, the Brazilian study cites to a January 1999 article by Professor Carskadon cautioning that students not versed in sleep requirements may see a start time delay as cause to work or play later in the evening. ⁽⁵⁾

“Moving the opening bell to a later time may help many teens with the mismatch between biological time and scholastic time, but it will not provide more hours in the day. It is not difficult to project that a large number of students see a later starting time as permission to stay up later at night studying, working, surfing the net, watching television, and so forth. Today’s teens know little about their sleep needs or about the biological timing system. Interestingly, students do know they are sleepy, but they do not have skills to cope with the issue, and many assume—just as adults do—that they are expected to function with an inadequate amount of sleep. This assumption is a physiological fallacy: sleep is not optional. Sleep is biologically obligatory. If students learn about sleep, they have a basis to use a changed school starting time to best advantage. Adding information about sleep to the school curriculum can certainly help.”  ⁽⁵⁾

In the intervening years, though few educators have added sleep science to the curriculum, their charges have nonetheless managed to acquit themselves nicely, demonstrating repeatedly that they use the additional time primarily for sleep, not Facebook. ^{(4, 30, 37, 41)} A recent study of New Zealand students ages 13-16 found that adding sleep science to the curriculum served to increase student sleep, but only on weekends, perhaps suggesting weekday sleep opportunities had already been maximized. ⁽⁶⁶⁶⁾ For the great majority of adolescent students, the later the school day begins, the longer they sleep. ⁽³⁰⁹⁾

  “Students in schools which have delayed their start times have not delayed their bedtime significantly but have been provided with the opportunity to obtain more sleep by sleeping later in the morning. This then provides a pathway whereby these students are better rested at school, have better attendance, and report better mood. Such policy changes may have a major impact on the health and education of adolescents.” ⁽⁶¹¹⁾

In 2005, Holy Cross Professor of Psychology Amy Wolfson, joined by Professor Carskadon, encouraged school administrators to “acknowledge the evidence and to adjust school schedules accordingly (e.g., delay high school start times).”  ^(12, see, n. 54 [ Wolfson & Carskadon among authors contributing to 2014 Am. Academy of Pediatrics middle and high school start time policy statement]; see also, ns. 30, 610.) Third, paying no mind to sleep, economists find that over the course of the school year, later starting students outperform their earlier starting peers academically, ^{(24, 49)} beginning in middle school and continuing through adolescence. ^{(44, 49)} Fourth, again without regard to sleep, scientific analysis of crash and traffic congestion data shows later starting students have significantly fewer car accidents than their earlier starting peers. ^{(46, 315, 420)}

Finally, setting aside certain facts for the moment (i.e., (i) ensuring appropriate bedtimes for minors is a parental function ⁽⁶⁶⁷⁾ benefiting both grade school and secondary school students, ^{(121, 122, 229, 314, 668)} and, (ii) homeschooled students awaken 18 minutes after public and private school students begin morning classes, obtaining 90 minutes more sleep per night), ⁽³⁰⁶⁾ as previously noted (§ IV, supra), CDC scientists report, “Delaying school start times is a demonstrated strategy to promote sufficient sleep among adolescents.” ⁽²⁶⁾

As discussed earlier (see, § IV.C., supra), CAREI researchers found that five years into their longitudinal study, students in Minneapolis high schools (8:40 a.m. start time) continued to get five more hours sleep per week than their peers in schools starting earlier in the day (7:30 a.m.). ^{(37, 341)} A 2007 study comparing two New England middle schools with different start times (7:15 a.m. vs. 8:37 a.m.) found similar bedtimes, but that by rising later, students at the later starting school obtained 50 minutes more sleep per night. ⁽³⁰⁾ Lead author, Professor Wolfson observed, “Students at later starting middle and high schools obtain more sleep due to later wake times and, in turn, function more effectively in school.” ⁽³⁰⁾

In 2008, physicians Zaw Htwe and Mary O’Malley of the Norwalk Hospital Sleep Disorders Center conducted a study of 259 high school students to determine changes in sleep duration following a start time change. When morning classes began at 7:35 a.m., the students averaged 7.03 hours per school night. ⁽⁴²⁾ When start times were delayed by 40 minutes to 8:15 a.m., the students slept 33 minutes longer per night. In other words, 83 percent of the extra time was utilized for sleep. ⁽⁴²⁾ The changes were consistent across all age groups. ⁽⁴²⁾ Bedtime on school nights was marginally later, and weekend night sleep time decreased slightly. ⁽⁴²⁾ More students reported “no problem” with sleepiness after the schedule change. ⁽⁴²⁾ The mean wake-up time prior to the delay was 6:12 a.m. Following the delay, students were able to “sleep in” to 6:53 a.m. ⁽⁴²⁾

As previously discussed (§ IV.C., supra), student participants in the 2009 Rhode Island study reported getting to bed 15 minutes earlier following the change to later start times, increasing their nightly sleep total by an average of 45 minutes. ^{(41, 669)} One student explained, “Well for me, ever since the 8:30 start, I have seen how much good 30 minutes of extra sleep does for me, so I have been inspired to … get an additional half hour on top of the 30 minutes.” ⁽⁴¹⁾

Boston University researchers report that following a 45-minute start time delay (7:30 a.m.-8:15 a.m.), surveys of tenth graders showed students getting to bed at the same time (10:36 p.m.), but rising 33 minutes later, at 6:53 a.m. instead of 6:22 a.m. ⁽⁵²⁴⁾ The number of students awakening independently (i.e., without assistance) increased from 6.8% to 15.7%. ^(524; see n. 535.5 [“The need for an alarm clock to wake up is a sign that they are not getting enough sleep at night.”].) Weeknight sleep increased to 8 hours, 17 minutes, ⁽⁵²⁴⁾ well short of optimal (~9.2 hours), more than borderline (8 hours), and less than adequate (~8.5 hours). ^{(12, 26)} 

The 2011 Israeli study of 14-year-old, eighth-grade students found that the teens slept about 55 minutes longer each night and performed better on tests when their start time was delayed by one hour, to 8:30 a.m. ^{(13, 352)} A recent study of Norwegian 10th graders found students got 66 minutes more sleep per night than students in a control group starting school one hour earlier, at 8:30 a.m. ⁽³⁵³⁾

A 2012 cross-cultural study comparing 302 U.S. adolescents (ages 13 to 19; M=16.03) and 385 Australian adolescents (ages 13 to 18; M=15.57) attending schools with 7:45 a.m. and mean 8:32 a.m. start times, respectively, found that on average, after controlling for age and sex, Australian students obtained 47 minutes more sleep per school night — precisely the difference in start times — than their U.S. peers. ⁽³¹⁴⁾ The 17.5% of Australian and 6.8% of U.S. students whose parents set bedtimes gained an average of 24 minutes sleep per night. ⁽³¹⁴⁾ Australian adolescents were more likely to have a later wake time (7:10 a.m. vs. 6:23 a.m.), and spend less time per day on extracurricular commitments (1 hr. 37 min. vs. 2 hr. 41 min.) than their U.S. peers. ⁽³¹⁴⁾

  “Previous studies using objective measures of sleep provide support for the notion that adolescents obtain more sleep when given the chance through a longer sleep opportunity…. Factors such as a later school start time, parental monitoring of bedtimes, and moderation in the number of hours spent on extracurricular activities are all likely to optimize sleep opportunity and so sleep. These factors have a cumulative effect. For adolescents who have a constellation of negative factors, such as an early school start time, no parent-set bedtime, and a heavy extracurricular load, the impact on their sleep and functioning is likely to be so detrimental as to present a significant negative impact. [¶] Findings of the present study are consistent with Bronfenbrenner’s ecological systems theory of human development and highlight the importance of taking a comprehensive approach to adolescent sleep…. Any factors that demand early rise times are likely to have a negative impact on sleep duration, particularly in light of the strong biological tendency of adolescents to delay sleep. This study provides further support that U.S. adolescents would benefit from later school start times.” ⁽³¹⁴⁾

In the fall of 2012, Jackson Hole High School in the Teton County School District No. 1 delayed its start time by 80 minutes, from 7:35 a.m. to 8:55 a.m. ⁽³⁰⁹⁾ CAREI researchers tracked student sleep before and after the start time change, finding the number of students capturing at least eight hours on weeknights increased by 20%, from 44.2% to 66.2%. ⁽³⁰⁹⁾

A 2014 Brown University study of 197 students (mean age = 15.6 years) at a “highly competitive” independent boarding school, found that following a modest start time delay, from 8 a.m. to 8:25 a.m., students captured an average of 29 additional minutes of sleep. ⁽¹⁰⁷⁾ The percent of students obtaining eight or more hours of sleep on school nights increased from 18% to 44%. ⁽¹⁰⁷⁾ The researchers found “noteworthy and concerning, that even after the delay in start time, very few students (8.8%) reported getting the recommended 9 or more hours of sleep.” ⁽¹⁰⁷⁾

Consistent with evidence establishing that the magnitude of the phase delay increases as children progress through adolescence, ^{(1.5, 20, 21, 65, 147, 193)} students in the upper grades (11th to 12th) received significantly less sleep than students in the lower grades; there was over an hour difference in the sleep duration of 9th graders compared with 12th graders. ^(107, see also, n. 145 [“Upperclassmen suffered a greater sleep deprivation.”].) “Thus, although this modest policy change yielded important and clinically meaningful improvements in sleep duration, it was not enough to overcome the chronic sleep debt experienced by this group of adolescents.” ⁽¹⁰⁷⁾ For all students, sleep duration decreased to baseline levels when the original school schedule resumed. ⁽¹⁰⁷⁾

A Yale University study published in early 2016 undertakes a systematic, meta-analytical review of start time studies meeting the following criteria: 1) published in English in a peer-reviewed journal; 2) available in full text; 3) primary or secondary school-aged youth were the subject of research; 4) experimental study design (i.e., randomized controlled trial, quasi-experimental, pre-post no control); 5) reported total sleep time; and 6) studies that examined the impact of delayed school start time on the same subjects. ^(43.5) Eighteen of 24 “articles” were excluded from consideration; i.e., observational, correlational, descriptive studies, technical reports, reviews, editorials, unpublished manuscripts, dissertations, and abstracts. ^(43.5) Participants’ mean age varied widely across the remaining six studies (ns. 13, 31, 41, 107, 353, 535), three of which are referenced briefly above, from 10.8 years to 16.4 years. ^(43.5) Participants in all but one study (n. 535) had a mean age of 13 years or older upon enrollment. ^(43.5)

The subject schools included two public high schools (ns. 31 [USA, grades 9-12]; 353 [Norway, grades 9-11]), one public middle school (n. 13 [Israel, grade 8]) one public primary school (n. 535 [China, grades 4-5]), and two private boarding schools (ns. 41 [USA, grades 9-12]; 107 [USA, grades 9-12]). ^(43.5) Despite the range of schools considered, all of the studies observed a significant increase in sleep duration. ^(43.5) Across the six qualifying studies, start time delays ranged from 25 to 60 minutes. ^(43.5) Total sleep time increased from 25 to 77 minutes, “suggesting a clinically meaningful dose response relationship.” ^(43.5)

“Importantly, among the studies that examined bedtimes and wake times, authors found delays only in wake times while bedtimes had either no change or were earlier. This provides evidence countering the hypothesis that students will simply stay awake later if school start time is delayed, and verifies the developmental shift in circadian timing that favors phase delay during later childhood. Increased sleep duration also contributed to reductions in daytime sleepiness (e.g., napping, overall sleepiness), which has implications for enhancing engagement in learning and achieving success in school due to improved cognitive functioning, problem solving, attention, decision-making, memory and creativity. Consistent with these explanations, our review found improved school-related outcomes following a delayed school start time intervention including decreased tardiness, presenteeism, falling asleep in class, being too tired to do homework, and improved reaction time; similar results have been observed in cross-sectional or observational studies employing a non-experimental design.” ^(43.5, citations omitted.)

Finally, a May 2016 CDC study reviewing 38 studies (cross-sectional or longitudinal) examining the association between school start times, sleep, and other outcomes among adolescent students, found that “[n]early all studies to date provide evidence that delaying school start time accomplishes the goal of increasing sleep duration among these students, primarily by delaying rise times. Most of the studies saw a significant increase in sleep duration even with relatively small delays in start times of half an hour or so.” ^(53.9)