The amount of time students spend in school is a popular lever of change pulled by education policymakers of all types. Longer days or shorter days; four-day weeks; starting school later in the morning; longer years or shorter years. Every permutation has been on the table at one time or another in recent years, with varying success. A study released this spring by Matt Kraft and Sarah Novicoff, and published as an Education Next article last month, takes a look at how much time kids actually spend in school in the U.S. these days. They compare these findings internationally and within U.S. states, while synthesizing what the best studies have to say about time use in education.
First, they identify and summarize findings from seventy-four U.S.-based studies that use credible designs—such as randomized controlled trials, difference-in-difference, and regression discontinuity—and that include effects on test scores, which is their primary measure. They look at studies pertaining to extending the total time in school and then compare differences in increasing that total time as part of the school day versus the year. They find that total instructional time has moderate to large effects on test scores, with more robust benefits accruing when it is part of a larger strategy to improve instructional quality, such as letting go underperforming teachers or increasing school level expenditures. In terms of extending the school year, adding ten or more extra days yields a small positive increase in achievement in math and English language arts (ELA) scores. As for lengthening the school day, they see small- to medium-sized positive effects on student achievement. The overall patterns are consistent but show diminishing returns to additional time tacked on to the day, with larger increases in time showing larger overall effects in education systems that have fewer total hours to begin with.
Next Kraft and Novicoff dig into international comparisons, using data collected in 2021 by the Organization for Economic Cooperation and Development (OECD), which captures instructional time in elementary schools across OECD member countries. Elementary schools in the U.S. are, on average, providing 1,022 hours of instructional time across 180 days in the school year, equating to 5.7 hours per day. This ranks us near the top of the distribution of instructional time: eighth among thirty-seven countries. The U.S. achieves this ranking through the combination of a relatively long school day (ranked eighth) but a short school year (tied for twenty-fourth). Fifteen countries have school calendars that are at least two weeks longer than the average 180 days in the U.S., including Spain, Greece, and France.
Digging deeper into the American context, as of February 2023, sixteen states mandate both the length of the school year and the number of total hours, while ten states give districts the freedom to meet a minimum number of either days or total hours. Eleven require only a minimum number of days, and thirteen only a minimum number of total hours. This results in vastly different minimum school time requirements based on where kids live.
Among the thirty-seven states that identify a minimum number of days, the majority (twenty-eight) set the bar at 180 days, but it ranges from a low of 160 in Colorado to a high of 186 in Kansas. Thirty-nine states specify a minimum number of hours per year, with high school hours ranging from 720 in Arizona to 1,260 in Texas. High school students in Alabama, Florida, and Connecticut are only required to have 900 hours of school per year, while their peers in Maryland are required to have 1,170. Students attending schools at the 90th percentile of the number of hours per day are in school more than an hour longer than those at the 10th percentile (7.50 versus 6.33 hours). Schools at the 90th percentile for the number of days per year are in session two weeks more than schools at the 10th percentile. Cumulatively, the total number of school hours per year differs by almost 200 hours between schools at the 90th and 10th percentiles—a gap that equates to approximately five and a half weeks of schooling, or more than two full school years over the course of a K–12 career (yikes!).
Finally, Kraft and Novicoff discuss the marginal returns of raising minimum time in school requirements. Of course, more time in school costs more money and the returns to student achievement eventually taper off. So policymakers should look to increase time in the places where it is most lacking.
And it should go without saying, but I’ll say it anyway: More time ineffectively used is a waste of time. And no one needs that.
SOURCE: Matthew Kraft and Sarah Novicoff, “Time in School: A Conceptual Framework, Synthesis of the Causal Research, and Empirical Exploration,” Annenberg Institute at Brown University (February 2024).
