Tuesday, November 22, 2016

How the Time of Day Affects Productivity: Evidence from School Schedules

Abstract—Increasing the efficiency of the school system is a primary focus of policymakers. I analyze how the time of day affects students’ productivity and if efficiency gains can be obtained by rearranging the order of tasks they perform throughout the school day. Using a panel data set of nearly 2 million sixth- through eleventh-grade students in Los Angeles County, I perform within-teacher, class type, and student estimation of the time-of-day effect on students’ learning as measured by GPA and state test scores. I find that given a school start time, students learn more in the morning than later in the school day. Having a morning instead of afternoon math or English class increases a student’s GPA by 0.072 (0.006) and 0.032 (0.006), respectively. A morning math class increases state test scores by an amount equivalent to increasing teacher quality by one-fourth standard deviation or half of the gender gap. Rearranging school schedules can lead to increased academic performance. 

I. Introduction 

Companies, schools, hospitals, and other organizations are always looking for innovations that increase productivity with little to no increase in inputs. History has proven that simple innovations such as assembly lines, crop rotation, washing hands, changes in incentive structures, and other simple managerial practices have been successful at increasing efficiency. By using such methods, companies increase their profits, hospitals improve patient outcomes, and schools produce more academically prepared students. 

In this paper, I propose a simple innovation that schools can use to improve student performance: rearranging schedules to take advantage of time-of-day effects. I use detailed, studentlevel panel data from the Los Angeles Unified School District for 1.8 million student-year observations. The data include the complete class schedule, grades, and California Standards Test (CST) scores for all sixth- through eleventh-grade students from 2003 to 2009. 

The fundamental challenge in estimating time-of-day effects is that class assignments are not random. Certain teachers or subjects might selectively be placed at certain times of day. The panel nature of the data allows me to control for individual characteristics, and the main results are estimated within teacher, class type, and student. The data allow previous years’ GPA and test scores to be used as clear falsification tests. These falsification tests, with the notable exception of English GPA, also support a causal interpretation of the results. I find that having math in the first two periods of the school day instead of the last two periods increases the math GPA of students by 0.072 (0.006) and increases math CST scores by 0.021 (0.003) standard deviations. These effect sizes are equivalent to increasing teacher quality by one-fourth standard deviation or half of the gender gap (Rockoff, 2004; Hyde et al., 2008). Similarly, having English in the morning increases the English GPA of students by 0.032 (0.006); however, there is no increase in their English CST score. There are no clear systematic differences in the time-of-day effect between boys and girls, older and younger students, students with high- and low-educated parents, or low- and high-performing students. The time-of-day effect may be caused by changes in teachers’ teaching quality, changes in students’ learning ability, or differential student attendance. The time-of-day effect may be interpreted as differential productivity during different parts of the day due to the circadian rhythm; stamina effects, with decreasing productivity the longer a student is at school; or school structure effects such as lower productivity after a lunch break. 

by Nolan G. Pope, The Revew of Economics and Statistics |  Read more (pdf):