When the school day starts later, teens get better sleep and feel more motivated

Getting out of bed is the first major hurdle of most teens' weekdays. Often assumed to be the product of laziness or moodiness, this difficulty rising in the morning is actually due to adolescent sleep patterns. During teenage years, circadian rhythms are relatively delayed, causing teenagers to both go to sleep and wake up later in the day.

Even so, schools in the UK still demand that teens attend lessons from 9am or earlier, while high schoolers in Germany or the USA may start as early as 7:30am. This holds students to early rise times that are more suited to those in other age groups.

In an attempt to compensate for lost sleep during the week, teens often oversleep on weekends and reduce their sleep overall. As poor sleep routines are associated with cardiovascular issues, mood disorders, substance abuse and more, it's easy to see why improving sleep in teens is an appealing target.

But what if school starting times worked with, rather than against, teenage sleep requirements? Research studies from years gone by indicate that such a change could be beneficial, but many lacked appropriate methods to measure potential effects of sleep interventions over longer periods of time.

This is precisely the gap that Anna Biller and colleagues in Germany endeavoured to fill with a recent study in Scientific Reports.

The team recruited students at a secondary school in Germany. This particular school has employed a "flexible system" since 2016, which allows students in grades 10 to 12 to postpone the start of their school day from 8AM to 8.50AM (or 10.15AM, on a day every two weeks when schedules allow it) as they please. Any morning study time lost to sleeping is regained by adding time after their last class of the day, or by filling gap periods already present in their schedule.

Data were collected in two waves, for six weeks immediately after the implementation of the flexible system and then again one year later. The team also took baseline measurements just before the system was introduced. 33 students participated in both waves, forming a longitudinal cohort.

In both waves, students completed a sleep diary noting when they fell asleep and woke up, their subjective sleep quality, and whether they had started school at 8AM or later. At the end of wave two, participating students also answered questions about their experiences and feelings surrounding the late start scheme.

Perhaps surprisingly, the uptake of late starts was quite low overall. By the end of the study, participants were only making use of a late start an average of just over one day per week. From student to student, uptake varied hugely — some would never use late starts, while others would use them every day.

When students did use later starts, however, they reported sleeping longer and better, getting closer to the optimal level of 8 hours of sleep. These benefits were near-universal, with 93% of students in the longitudinal cohort reporting longer sleep on late start days in both the first and second wave. On these days, participants also reported improved sleep quality, and were more likely to report waking naturally before their alarm.

A clear gender difference also emerged. In the first year, both boys and girls stuck to their usual bedtimes while using the flexible start. But a year later, boys were more likely to take the opportunity to postpone their sleep onset, resulting in sleep gains falling from 1.3 hours to just 30 minutes. The authors believe that this split in behaviour may have been a factor in previous research's mixed findings.

However, the flexible system didn't produce a significant improvement in students' overall sleep across the entire week. The team believe that this is due to the low uptake of the late start scheme. Though on paper a later start might sound appealing, students listed many reasons that they preferred to start earlier, such as difficulty getting to school later.

Another paper from the same study also showed no improvement in grades for students who favoured waking later — though the team believe that grades are arguably not an ideal proxy through which to see improvements. Despite this, the current paper did provide clear evidence of other kinds of benefits: not only did the students enjoy getting to school later on late-start days, they also felt more motivated and able to concentrate, and reported greater sense of wellbeing.

This study was conducted at the most academic type of German secondary school, equivalent to a grammar school, which limits the generalisability of the findings. It's possible, perhaps even likely, that students from other backgrounds or countries will experience different costs and benefits when taking advantage of late starts.

As appealing as later school starts may sound, their practicality and effects on students within the UK system requires further investigation. Apologies to younger readers!

Further reading

– Sleep improvements on days with later school starts persist after 1 year in a flexible start system

About the author

Post written for BPS Research Digest by Emma L. Barratt (@E_Barratt). Emma is a cognitive scientist and science communicator based in Newcastle, UK. Her work centres primarily around atypical and clinical psychology, as well as cognitive factors pertaining to human spaceflight and space exploration. In 2015, she published the first peer reviewed investigations of Autonomous Sensory Meridian Response. She also works alongside an international team to produce educational content for the popular YouTube channel SciShow.