NEW: Expanded Analysis of High School Start Times in Missouri
A Look At 497 High School Start Times Across the State
By : Courtney Vahle, Ed.D.
Published On: August 6, 2025
Last year, PRiME compiled a first-of-its-kind, comprehensive dataset of Missouri high school start times, containing 230 school districts (50% of school districts educating 80% of the state’s students).
This year, we were able to expand our analysis to 497 high schools from 432 school districts and charter LEAs across the state (93% of the state’s school districts educating 97% of Missouri public high school students) for a more comprehensive view of the high school start time landscape in Missouri.
The American Academy of Pediatrics (AAP) supports delaying the start of the school day for middle and high school students to 8:30 AM or later to allow students the opportunity to meet their growing sleep needs in adolescence. Other research indicates delayed start times may increase academic performance and attendance and decrease tardiness.
Opponents to changing start times cite complicated bussing schedules, increased transportation and care costs, and interference with extracurriculars, parents’ schedules, and more.
The results of the August 2024 SLU/YouGov Poll overwhelmingly suggest Missouri voters are in favor of pushing back start times (52% support overall), particularly those voters aged 18–44, who are more likely to have school-aged children (more than 71% support).
Missouri high schools have the 11th earliest start in the nation. Our analysis shows the statewide average start time to be 7:52 AM, a full 38 minutes earlier than the recommendation.
Missouri High School Start Times
Average Missouri High School Start Times by Region
Some schools in our sample start classes as early as 7:00 AM. At present, just 3% of Missouri high schools begin class at 8:30 AM or later, and 12% begin class before 7:30 AM.
Schools in two major urban centers in the state (STL and KC) had earlier average start times than schools in the Central region of the state by nearly one half hour.
There is not a significant difference between the start times in charter and regular local schools, although the sample is small (there are only 16 charter schools in Missouri who educate high-schoolers). Moreover, charters are, by law, only allowed to operate in the urban centers of the state, which we know had overall earlier start times.
Schools who run a 4-day school week have an average start time just three minutes earlier than schools with a 5-day school week; the additional school hours are added to the end of the day. Interestingly, students attending schools with four-day weeks in our sample attended school just 34 minutes longer per day than students attending 5-day school week schools. Thus, on average, high schools with 5-day weeks had students attending 4 hours and 52 minutes longer per week. Although this time accounts for an extra lunch, morning announcements, and passing periods, there is still room to consider which parts of the day may be able to be cut or shortened to accommodate a later start.
Districts, communities, parents, and legislators should evaluate the research and analyze the school start times in their own district. They should carefully weigh the costs and benefits of school start times for each group of students.
To read the full analysis, click here: https://www.primecenter.org/policy-brief-database/early-risers
The PRiME Center provides an updated analysis of high school start times across the state of Missouri.