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Adolescents are chronically sleep deprived on school days, which negatively impacts their well-being and ability to learn. A new study conducted by the University of Zurich and the University Children’s Hospital Zurich reveals that a flexible start to the school day can improve adolescents’ sleep, health and academic performance.
High school students often have trouble getting to bed at a reasonable time, which makes it difficult for them to start school early in the morning. This is because teenagers are biologically wired to fall asleep later than adults, with their biological clock shifting progressively later throughout adolescence. The result is that most teenagers don’t get enough sleep on school days, and their sleep deficits increase as the week progresses.
“This is concerning, as chronic sleep deprivation not only affects well-being, but also has a measurable impact on mental health, physical development and the ability to learn,” says Oskar Jenni of the University of Zurich (UZH). According to Jenni, a developmental pediatrician, adolescent sleep biology prevents them from falling asleep early enough to meet their sleep need, so starting school later in the morning could have significant positive effects. While the impact of beginning the school day later has been well-studied internationally, there is currently a lack of research on flexible models that allow students to choose between an early and a later start.
New school model with flexible start and end times
Joëlle Albrecht, Reto Huber and Oskar Jenni from the University of Zurich and the University Children’s Hospital Zurich have now conducted research that provides scientific backing for school schedules that are better adapted to teenagers’ needs. Three years ago, the Gossau Upper Secondary School in the northeastern canton of St. Gallen introduced flexible school hours. Since then, students have had the option to attend modules before regular classes begin in the morning, at midday and in the afternoon. This means students decide when they start their school day: they can arrive at 7:30am or wait until 8:30am, when classes officially begin.
Using this model, the research team examined the sleep patterns of adolescents and the impact of sleep deprivation on their health and academic performance. The pupils, who were 14 years old on average, were surveyed once under the old school model, with a 7:20am start, and a second time a year later under the new model. The research team evaluated 754 responses in total.
Flexible school schedules allow for more sleep
The findings are unequivocal: 95% of students took advantage of the option to start school later – on average, 38 minutes later than under the old system. As a result, the teenagers were able to get up 40 minutes later in the morning. Because they continued to go to bed around the same time, their total amount of sleep increased: on school days, the students slept an average of 45 minutes longer.
There were also other advantages. “The students reported fewer problems falling asleep, and health-related quality of life increased ,” summarizes lead author Joëlle Albrecht. Under the new model, objective learning outcomes in English and mathematics improved compared to cantonal test results.
Improved health and academic performance
The study, published in the renowned Journal of Adolescent Health, shows that flexible school start times can be an effective and practical approach to reducing chronic sleep deprivation and improving adolescents’ mental health and academic performance. “Starting classes later in the morning can therefore significantly contribute to addressing the current mental health crisis among pupils,” adds co-author Reto Huber. In 2022, a study published by the Swiss Health Observatory (Obsan) found that 47% of 11- to 15-year-olds experienced multiple recurring or chronic psycho-affective complaints, such as sadness, fatigue, anxiety, low mood, tension, irritability, anger and difficulty falling asleep.
Contact:
Dr. phil. Joëlle Albrecht
Developmental Pediatrics, University Children’s Hospital Zurich
joelle.albrecht@kispi.uzh.ch
+41 79 657 15 85
Prof. Dr. sc. nat. Reto Huber
Developmental Pediatrics, University Children’s Hospital Zurich
Child and Adolescent Psychiatry, University Hospital of Psychiatry Zurich, University of Zurich
reto.huber@kispi.uzh.ch
+41 44 266 81 60
Prof. Dr. med. Oskar Jenni
Developmental Pediatrics, University Children’s Hospital Zurich
oskar.jenni@kispi.uzh.ch
+ 41 44 249 75 36
Literature
Albrecht, J. N., Risch, A., Huber, R., & Jenni, O. G. (2026). The power of flexible school start times: Longitudinal associations with sleep, health, and academic performance. Journal of Adolescent Health, 17 February 2026. DOI: 10.1016/j.jadohealth.2026.01.011
https://www.news.uzh.ch/en/articles/media/2026/school-later.html
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