Late start times benefit high school students

A blackboard

It’s no secret that high school–aged teens are happier—or at least less bedraggled—when they’re allowed to sleep in a bit in the morning. Now the numbers are offering proof as to just how precious that sleep can be.

According to a new University of Minnesota study released this week, later high school start times improve both student grades and overall health.

The three-year research project, using data from more than 9,000 students attending eight high schools in three states, found that when switching to a later start time:

• school attendance, standardized test scores, and academic performance in math, English, science and social studies improved, and

• tardiness, substance abuse, symptoms of depression, and consumption of caffeinated drinks decreased.

In addition, the study found that there was a whopping 70 percent drop in the number of car crashes involving teen drivers at Jackson Hole High School in Wyoming, which shifted to the latest start time of the eight schools (8:55 a.m.).

Confirming the benefits of sleep

"The research confirmed what has been suspected for some time," says Kyla Wahlstrom, director of the U’s Center for Applied Research and Educational Improvement (CAREI), which conducted the study. "High schools across the country that have later start times show significant improvements in many areas.”

The study, funded by the Centers for Disease Control and Prevention (CDC), found that high schools that begin as late as 8:55 a.m. have 66 percent of students obtaining eight or more hours of sleep on school nights, which is the recommended amount for high school–aged students.

A start time of 8:35 a.m. allows 57-60 percent of students to get eight or more hours of sleep, but schools that begin at 7:30 a.m. have an average of only 34 percent of students sleeping eight or more hours on school nights.

“Eight hours of sleep seems to be the tipping point for making healthy choices,” says Wahlstrom, who has been studying school start times for 17 years. With the later start time, “you have double the amount of kids getting eight hours or more of sleep and making healthy choices as a result.”

The decrease in car accidents near Jackson Hole High School was a real eye opener for Wahlstrom, and she points to a similar number at Mahtomedi High School, where the number of crashes involving drivers ages 16-18 fell by 65 percent. 

“The reduction of teen car crashes may be the most important finding of all, as the well-being of teens and the safety of the general public are interrelated,” she says. “From a public health standpoint, it’s pretty important.”

Students examined in three states

The study was the first to examine multiple schools in various locations across the United States. Data were collected from eight schools that moved to later start times. Researchers surveyed St. Louis Park High School, Mahtomedi High School, Woodbury High School, Park High School, and East Ridge High School in Minnesota; Boulder High School and Fairview High School in Colorado; and Jackson Hole High School in Wyoming.

Students were individually questioned about their daily activities, substance use, and sleep habits. Researchers then examined various health factors after the change in school start time and compared them with national average data.

The study also collected comparative data about students’ academic performance, including grades, attendance, tardiness, and performance on state and national standardized tests. The car crash data were examined for the communities surrounding the participating high schools.

"Our research provides evidence of clear benefits for students whose high schools start at 8:30 a.m. or later," says Wahlstrom. "More research needs to be done, but these findings are substantive and should provide more information for school districts considering a change in start time."

Learn more about school start time research and teens and sleep resources at CAREI.

Night owls by nature
When it comes to ensuring that high school students get a good night's sleep, it's not simply a matter of having them go to bed early, says Wahlstrom. Their bodies don't begin to secrete melatonin, the hormone that helps induce sleep, until the monologues are wrapping up on the late-night talk shows.
“Biologically, the medical research shows that teenagers are incapable of falling asleep before 10:45,” she says.

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