Later School Start Times

“Mind, Body, Sleep” SBSM Blog Post January 2020 

California becomes the first state to officially promote later school start times and better sleep habits among teenage students. By July 1st, 2022, public middle schools will start no earlier than 8:00am, while high schools will start no earlier than 8:30am.  

The Society of Behavioral Sleep Medicine (SBSM) interviewed Julie Dahl, APRN, the president of the Minnesota Sleep Society. Julie explains the science behind the start school later movement in our podcast interview.  Click here to listen to the podcast.  Highlights from the interview are noted below. 

How many hours of sleep do teenagers need?

According to American Academy of Sleep Medicine (AASM), it is recommended that “teenagers, 13 to 18 years of age, should sleep 8 to 10 hours per 24 hours on a regular basis to promote optimal health and daytime alertness during the critical transition from childhood to adulthood.” 

Additionally, the National Sleep Foundation recommends 7:00am to be the earliest wake-up time for teenagers. “7:00am for teenagers is like 4:00am for adults.”  

Julie points out that teenagers can be night owls by nature. It is quite normal for growing teens to want to sleep late and sleep more in the morning.  

What are some benefits for a later school start time?

During a 3-year research study, which involved over 9000 students from eight public high schools across three different states, researchers found the following results:

  1. Within the schools with a start time after 8:30am, 60% of students received over 8 hours of sleep per school night. 
  2. For teenagers getting more than 8 hours of sleep: Many reported decreased depression symptoms, less use of caffeine, and lower risk of using illegal substances.
  3. For teenagers with a school start time of 8:35am or later, academic performance outcomes and attendance rates were improved while tardiness was reduced.
  4. The rate of teen driver car accidents dropped significantly after the school start time shifted to a later time. 

Later school start times are also associated with improvements in sports performance, reduction in sports injuries, and reduced need for sleep on the weekends. 

What can parents and teenagers do to help optimize sleep?

Julie suggests that the practice of a later school start time should be combined with a sleep education program. She encourages parents and teenagers to watch for signs of lack of sleep, such as grumpiness, poor grades, and/or difficulty waking up in the morning. Parents may want to help their teen(s) make sure to allow enough time for sleep and arrange family priorities around sleep time. Julie encourages teens to “wind-down” both body and mind about 1 to 2 hours before bedtime.  

How can you find more resources and information about this topic?

Julie shares some great resources during our interview.   Click here to view these resources.  For parents, this FAQ sheet and the Evidence Summary section of the Minnesota Sleep Society Teen Sleep Loss Toolkit, may be useful. To advocate for later school start times in your area, visit Start School Later.  


 AASM website:

Wahlstrom, K., Dretzke, B., Gordon, M., Peterson, K., Edwards, K., & Gdula, J. (2014). Examining the impact of later high school start times on the health and academic performance of high school students: a multi-site study.

National Sleep Foundation:

Minnesota Sleep Society:

FAQ Sheet:

Evidence SUmmary:

Sleep Loss Toolkit:

Start School Later: 


Yishan Xu, PhD
Licensed Clinical Psychologist (Mandarin & English)
Psychotherapy & Assessment Group Practice
Mind & Body Garden Psychology Inc

Thank you Julie Dahl, APRN for your time and contribution to this post.