Chronotype, School Schedules, and Academic Achievement

Source: Pixabay free images

Chronotype is the behavioral manifestation of many underlying physiological processes. Those who wake up and go to sleep relatively early are Morning Types, while Evening Types go to sleep and wake up later. Chronotypes reflect a normal distribution (bell-shaped curve) such that most people are in the middle and fewer are at the extreme ends. There are brief questionnaires to determine one’s type, but most people don’t need to complete one to know their type. Chronotypes have been shown to change over age, with children tending to be Morning Types, then becoming more Evening Types during adolescence, and returning to Morning Types in late adult years. One’s chronotype is established in part by biological processes that are influenced genetically, and in part by environmental factors including school and work schedules.

Sleep scientists have argued that school starts too early for middle and high school students due pimarily to the shift in chronotype that occurs around the onset of puberty. This shift is also referred to as a Phase Delay because delays in natural melatonin release make it more difficult to go to sleep early enough to get sufficient sleep with subsequent sleepiness in the morning. Sleepiness in the early hours of school then often results in tardiness, academic underachievement, and behavior problems. The assumption is that starting school later will mitigate these negative outcomes. Among the questions raised are:

1. Will students actually get more sleep? (Some argue that they will simply stay up later with no increase in sleep.)
2. If they do get more sleep, will this change result in better outcomes?
3. If there are better outcomes, will they endure after students habituate to the novelty of the change?

While many studies have been conducted to answer these questions, all but a rare few have not been able to provide the definitive proof necessary to establish cause and effect. The strongest proof comes from conducting a Randomized Control Trial. In this case, students would have to be assigned randomly to either the present early start schedule (the Control condition) or to the later start schedule (the Experimental condition). In drug efficacy studies, participants should not know (or are “blind”) to which condition they have been assigned — either the placebo condition where they take a sugar pill — or the experimental condition where they take the new drug. This procedure is required to control for the expectancy effect, a psychological phenomenon by which research participants expecting to attain the desired effect (such as diminished symptoms of illness) report that the drug worked for them. A “double-blind” procedure is ideal in which neither the participants nor the researchers who analyze the data know which participant is in which group.

In studies of the effects of school start times, among the problems that prevent clear conclusions are:

1. Students are not randomly assigned to either early or later school start times.
2. The conditions occur for all students consecutively in one direction (earlier then later; rarely if ever later then earlier) rather than simultaneously where both a control and experimental group would begin at the same time.
3. Students obviously know what time school starts, so that even a randomized trial has some inevitable limitations.

A study published in 2020 by a group of researchers in Argentina is one of the best experiments to date for answering some of the questions. Students in a Buenos Aires high school were assigned by lottery to one of three school schedules: 7:45 AM – 12:05 PM; 12:20 PM – 5:00 PM; 5:20 PM – 9:40 PM. Students self-reported their chronotype by completing a Mornngness-Eveningness questionnaire and also reported bedtime, wake times, and sleep durations for both weekdays and weekends. Grades were assigned for each subject four times a year and by two comprehensive exams given at different times during the year. Separate analyses were done for younger (13-14) and older (17-18) students.

The results were as follows:

1. Morning attending students with earlier chronotypes outperformed later chronotypes in all subjects, with the largest difference in mathematics.
2. For students attending in the early afternoon, there was no difference in grades by chronotype.
3. Students with later chronotypes who attended in late afternoon/evening performed better than students with later chronotypes who attended at earlier times.

The authors conclude that students perform best when their chronotype is more in synchrony with the start of school and that the best results may be possible when start times are progressively delayed by age with older students starting last. Further, based on the finding regarding math, they suggest that offering math classes later in the day may be beneficial. It is important to remember, however, that most but not all younger students are Morning Types and that most but not all older students are Evening Types. So while the performance of each age group might be on average better with synchrony, there would still be some proportion of high school students who are Morning Types and would show no benefit with later start times.

Much research on sleep in children and adolescents was begun in Spring 2020, when many schools discontinued in-person classes, and the studies are continuing now. Online instruction is sometimes more flexible in start time, and with the time needed to commute to school eliminated, even with an early online start students would be able to sleep a little later. Results of those studies are being published regularly and they will further inform us about optimal times for different age groups and different chronotypes. If students taking classes online have some choice about when they begin and when classes for different subjects occur, then more synchrony can possibly be attained. In some cases, such flexibility is limited when start times for lessons conducted in real time are fixed by the school. The exceptional circumstances of the past and coming school years will provide additional information for students, parents, and schools regarding the optimal timing of classes.