When teens complain that school starts too early, they’re not wrong, according to new research.

This comes as school districts across the country—including in Colorado, California, Indiana, and Tennesseeconsider starting school later.

The study, published last month in the peer-reviewed Journal of Human Resources, looks at districts in Florida and uses a novel approach: the fact that some areas in the state operate in the Central time zone while others use Eastern time. That means that if one district starts school at 8 a.m. Eastern and one right next door starts at 8 a.m. Central, students are actually heading to school at different times, relative to the sunrise—creating a natural experiment for the researchers to study how that affects student achievement.

Study authors Jennifer Heissel and Samuel Norris of Northwestern University followed students who move between schools in different time zones; they expected that students going from Eastern Time to Central Time will see their test scores improve because they get more sunlight prior to school.

In fact, that’s exactly what they found, particularly for older students. When an older student moved to a district that starts school later, their standardized test scores improved in the year they move and in later years. The effects are notable, but not huge: roughly equivalent to the impact of a substantial reduction in class size.

A doughnut chart showing 9.5 percent of public high schools started before 7:30 a.m. in 2011-12, 33 percent started between 7:30 a.m. and 7:59 a.m., 43.1 percent started between 8 a.m. and 8:29 a.m., 10.6 percent began between 8:30 a.m. and 8:59 a.m., and the remainder started after 9 a.m.
(Ntl. Center for Education Statistics / Chalkbeat)

The research finds that is driven by the changes in ideal sleep patterns caused by entering puberty. That means girls are negatively impacted by late start times starting around age 11, and boys at age 13.

The study posits a straightforward way to improve student achievement without changing a district’s average start time: ensuring that a district’s high schools start the latest and elementary schools the earliest. Most Florida districts examined don’t do that, but if they did, the researchers estimate that it would improve average test scores.

Those results are consistent with past research, which has driven past efforts to start school later. As the authors point out, the American Academy of Pediatrics recommends starting high school no earlier than 8:30 a.m., but as of 2012, the average start time for an American high schools was 7:59 a.m., with the vast majority beginning before 8:30 a.m..

One Colorado school district, Cherry Creek, currently starts at 9 a.m. for elementary school, 8 a.m. for middle school, and 7 a.m. for high school—precisely the opposite order that the research would suggest is ideal for improving achievement. The district just approved a move that would start elementary school earlier and middle and high school later.

When schools try to change start times, though, they run into logistical challenges: parents’ work schedules, sports event timing, bus coordination, and before- and after-school activities.

Indeed, the change in Cherry Creek garnered protest from parents, although an online survey of students and staff showed support for the changes, according to the district.

“If the new start time is adopted, young children will be waiting at the bus stops or walking to school in the dark/dawn during some months of the year,” according to a Change.org petition opposing the change. “This is unsafe for our young children.”


This post appears courtesy of Chalkbeat.