Advocates for starting school later in the morning often assert that letting kids sleep in has been proven to improve academic performance but I was surprised to learn how murky the research evidence is. 

A new Minnesota study of 38,000 students slightly bolsters the evidence for starting school later but isn’t quite the knockout punch that advocates hoped to make. 

The study, “Changes in school start time have a significant effect in the amount of sleep and reported grade point average of students,” was conducted by researchers at the University of Minnesota and the Bloomington, Minnesota, public schools and was presented in April 2021 at a session of the annual meeting of the American Educational Research Association. 

• Student grades increased a little, raising students’ grade point averages by an extra 0.1 points, on average, after schools delayed start times. 

• After the switch in start times, students were 16 percent more likely to meet the recommended hours of sleep, which is nine or more hours for students in grades 5 and 8 and at least eight hours for students in grades 9 and 11.

• There seems to be no harm to children in switching to a later school start but there are many obstacles, including bus schedules, and the start time of after-school sports. 

1. Caesar, J., Lamm, R., Rodriguez, M. C., & Heistad, D. J. (2021, April 10). Changes in school start time have a significant effect in the amount of sleep and reported grade point average of students [Paper presentation]. American Educational Research Association Annual Meeting. 
2. Sabia, J. J., Wang, K., Cesur, R., & Sabia, J. J. (2017). Sleepwalking through school: New evidence on sleep and academic performance. Contemporary Economic Policy, 35(2), 331-344.  
3. Sawyer, H., & Taie, S. (2020). Start time for U.S. public high schools. National Center for Education Statistics, U.S. Department of Education. 
4. Dunster, G. P., Iglesia, L. De, Ben-hamo, M., Nave, C., Fleischer, J. G., Panda, S., & Iglesia, H. O. De. (2018). Sleep more in Seattle: Later school start times are associated with more sleep and better performance in high school students. Science Advances, 4(12), 1–7. 
5. Dupuis, D. N. (2015). The association between elementary school start time and students’ academic achievement in Wayzata Public Schools. Center for Applied Research and Educational Improvement. University of Minnesota.