Later high school start times improve student grades and overall health, according to a new College of Education and Human Development study.

The three-year 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:

• attendance, standardized test scores and academic performance in math, English, science and social studies improved.
• tardiness, substance abuse, symptoms of depression, and consumption of caffeinated drinks decreased.

In addition, the study found that there was a 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.).

“The research confirmed what has been suspected for some time,” said Kyla Wahlstrom, Ph.D., director of the 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 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.”

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. Schools that begin at 7:30 a.m. have an average of only 34 percent of students obtaining eight or more hours of sleep on school nights.

“Even a start time of 8:35 a.m. allows 57-60 percent of students to get eight or more hours of sleep, which is an important health benefit for a majority of students,” said Wahlstrom. “Local school districts, school personnel, parents, and students need to understand the importance of sleep and to make choices using the knowledge from this and other studies.”

In the first study to examine multiple schools in various locations across the U.S., student data were collected from eight schools that moved to later start times. Over the last three years, 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 surveyed about their daily activities, substance use and sleep habits. Researchers then examined various health factors post-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. Car crash data were also examined for the communities surrounding the participating high schools.

The full report, “Examining the Impact of Later High School Start Times on the Health and Academic Performance of High School Students: A Multi-Site Study,” includes an examination of the processes by which local school districts participating in the study made the decision to change to a later start time. Key participants in the discussions and the decision-making were interviewed.

“Our research provides evidence of clear benefits for students whose high schools start at 8:30 a.m. or later,” said 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.”

See more research on teens and sleep. Also see coverage of this new study in the New York Times, HuffPost Live, Star Tribune, KSTP-TV, KARE 11-TV, and more media outlets.