Early vs. Late School Start Times: How They Affect Students Physically

Many parents recall times when they had to pound on their children’s doors or go so far as to drag them out of bed when it was time to get ready for school. While most people chuckle when they hear these stories, the reason behind them isn’t so funny. Many adolescents actually experience sleep deprivation due to early school start times. Some adolescents have to wake up at 4:00 or 5:00 in the morning just to catch the bus and make it to school on time. During a time when the body needs more than eight hours of sleep each night, ongoing sleep deprivation can have serious physical effects.

The Adolescent Sleep Cycle

Parents know that young children are often up with the sun, causing everyone in the house to wake up earlier than usual. This changes once a child enters adolescence. While most young children awaken early without an alarm clock or wake-up call, adolescents need every minute of sleep they can get. This is due to the way adolescent bodies produce and secrete melatonin, the hormone that helps regulate the sleep cycle. Increased melatonin levels during the early morning hours make it difficult for adolescents to wake up and get moving.

Sleep Deprivation

Sleep deprivation is when someone fails to get enough sleep at night. The American Academy of Sleep Medicine says that adolescents have an increased risk of sleep deprivation because they experience restricted sleep times. If a teen participates in after-school activities such as sports or music groups, homework and study time end up taking place after dinner. This means adolescents may stay up until 11:00 or later to finish all of their work. Going to bed at 11:00 and getting up at 5:00 for school means that a teen is not getting enough sleep.

Increased Blood Pressure

Dr. Sheldon Sheps from the Mayo Clinic says that sleeping fewer than six hours per night may increase blood pressure. The body uses sleep as an opportunity to regulate stress hormones such as cortisol. The body also needs sleep to maintain the nervous system properly. When an adolescent does not get enough sleep, the body does not have the opportunity to keep up with this maintenance. Increased levels of stress hormones lead to increased blood pressure. Later school start times prevent sleep deprivation, which also prevents increased levels of stress hormones in the blood. This reduces the risk of high blood pressure, helping adolescents preserve their health.

Diabetes Complications

Teens with diabetes are at risk for serious complications if they do not get enough sleep. There are several factors at play in adolescents who are diabetics. One is that high blood sugar levels prompt the kidneys to eliminate the extra sugar by triggering urination. When this occurs at night, it results in interrupted sleep. Sleep-deprived diabetics may try to gain energy by eating foods high in sugar. This results in elevated blood glucose levels, which cause blood vessel damage and other complications if the problem occurs on a regular basis. Dr. Mark Mahowald of the Minnesota Regional Sleep Disorders Center reports that lack of sleep may even lead to pre-diabetes in some people. Later school start times allow adolescent diabetics to get at least an extra hour of sleep each night. This can prevent late-night eating and blood sugar spikes, reducing the risk of diabetic complications.


The obesity epidemic among children and teens may be due, in part, to a lack of sleep. The National Health and Nutrition Examination Survey I followed more than 9,000 people from 1982 to 1984. Part of this study involved weighing each participant. Those who reported getting fewer than seven hours of sleep per night were more likely to be obese at the beginning of the study. Participants getting only six hours of sleep each night were 27 percent more likely to develop obesity than those who got seven to nine hours of sleep each night. Participants who slept only two to four hours each night were 67 percent more likely to develop obesity.

The lack of nutritious school lunch options combined with sleep deprivation and reduced physical activity put adolescents more at risk for obesity than ever. One complication of obesity is sleep apnea. Obstructive sleep apnea causes brief pauses in breathing during the night, which can have serious effects on an adolescent’s health. Sleep apnea increases the risk of sudden death and causes fatigue, headache and other problems. Starting school later in the day reduces the risk of developing obesity as a side effect of sleep deprivation. Students who get more sleep tend to weigh less than students who do not.


One of the most common effects of sleep deprivation is fatigue. Fatigue is an overall lack of energy throughout the day. Sleep-deprived adolescents may have difficulty getting enough energy to study, complete homework assignments, complete school projects and participate in extracurricular activities. Prolonged fatigue is especially dangerous for older adolescents who drive to school, work, and social activities. Fatigue increases the risk for crashes, which increases the risk of injury and death. Later school start times give adolescents more of an opportunity to rest and recharge, reducing fatigue and helping prevent teen auto crashes. Reduced fatigue also leads to more energy and alertness, which has the added benefit of improving school performance in some adolescents.

Parents and teens should talk to their doctors to determine the right amount of sleep to get each night. The answer varies based on several factors, one of which is activity level. Someone who lives a rather sedentary life might need less sleep than an adolescent who plays football or goes to marching band practice for three hours every night. The right amount of sleep also depends on how an adolescent feels each morning. If a teen gets 7.5 hours of sleep and feels rested and alert, then this is enough sleep for that teen. If someone else only feels well-rested after nine hours of sleep, then nine hours of sleep per night is the right amount for that person. Later school start times can help prevent sleep deprivation and allow adolescents to attend school when their minds and bodies are at peak performance.

About Leigh Ann Morgan

I write about all sorts of things but ever since I completely got rid of my constant neck pain by finding the perfect pillow, I've started to learn as much as I can about sleep quality and sleep disorders.


  1. Given this information, and the equally strong research about the circadian rhythms of adolescents and young adults, I don’t see how we can continue to start middle and high schools so early in the morning. The numbers just don’t add up when it comes to hours left to sleep – even if you cut all electronics, extracurriculars, and any form of social life out of the equation – and, frankly, it’s negligent to continue prioritize adult convenience or illusory cost savings over the short- and longterm health of the students.

    We’re taking action at StartSchoolLater.net, and our petition requesting a legislated MINIMUM school start time has reached almost half the number of signatures needed. I urge anyone who cares about this issue to join us by signing the petition at http://signon.org/sign/promote-legislation-to.fb1?source=s.fb&r_by=1521139 . For more information about the growing national coalition of health professionals, sleep scientists, educators, parents, and other citizens unwilling to subject another generation to inhumane, dangerous, and counterproductive school start times, see StartSchoolLater.net

  2. Thank you for this article – it makes the case so clearly, yet people continue to stubbornly stick to what they know. High school kids are seriously exhausted and I worry about the long-term impacts on their physical and mental health. My daughter is a freshman in high school and she wakes up at 5:45 to catch a 6:25 bus to get her to school for 7:17 start time. Until recently, this whole trip took place in the dark! It’s amazing to me that we, as a society, are allowing this!!

    Please sign the petition to ask for a legislated minimum start time. This is an issue that ranks up there with clean water, safe school buildings, and other nationally regulated health and safety guidelines. It takes one minute to sign up – and the petition provides an easy way to pass it on to email, facebook and twitter. Join us!