This article by Mary Beth Walker, Dean of the Andrew Young School of Policy Studies at Georgia State University, is being reprinted here with permission from the author and Creative Commons:

How would you react if you were told that your local public school planned to change the schedule from the traditional Monday-through-Friday model to a schedule that contained four longer school days? Would you worry about long days for young children, their academic accomplishments and, of course, childcare?

Across the US many public school districts have considered the option of schedule change as a way to manage budget cuts and re-allocations. A surprising number of schools, especially in the western United States, have adopted just such a policy. In most cases, students in these schools now attend school Monday through Thursday.

Parents can easily imagine that young children would suffer from longer school days. Also, children of all ages could have too many opportunities to forget what they had learned over a three-day weekend.
So, what impact is the four-day-week schedule actually having on student achievement?
Mark Anderson, a faculty member at Montana State University, and I embarked on a study to examine the impact of the four-day week on student learning. Our results show a positive impact on student achievement.

Here’s how we did our study:  When we started, we found only few evaluations of the policy change had been carried out. Furthermore, most evidence was anecdotal and simply described the changes in a single district.

We found these descriptions to be unsatisfactory. It allowed for too many other factors that could influence student performance, other than a district’s decision to switch schedules.

For example, if the four-day schedule were adopted in school districts where scores were already going up, the existing trend would confound the effect of the schedule change.

We were not able to do a large-scale experiment whereby we could assign some children to four-day schedules and some others to traditional schedules to examine the impact. But we did the next best thing.

A four-day week was seen to have a positive impact on reading and math scores. US Department of Education, CC BY.

We gathered data over time for schools that had adopted a four-day week and then we chose a “matched” sample of schools that had stuck with a traditional five-day week.

The schools were “matched” in terms of size and school characteristics, as well as socioeconomic characteristics such as ethnicity and free- and reduced-lunch enrollment.

We could then examine average grade achievement on the state‐mandated tests over a longer period and compare changes in achievement for the four-day-week schools versus the traditional-schedule schools.

In order to avoid the problems in comparing state achievement scores across states, we used data only from schools in Colorado, where over one‐third of the school districts have adopted the four‐day schedule.

What did we find? Our results, based on fifth grade mathematics scores, generally show that achievement rises after the introduction of a four-day week. We found that, even after we take into account the variations due to different socioeconomic levels, the four-day school week is associated with an increased achievement.

We found that, on average, math scores increased by about seven points, meaning that the percentage of fifth graders scoring either proficient or advanced in mathematics went up from about 60% to about 67%, after the schedule change to a four-day week.

These results were statistically significant, meaning there is a very low probability that the results occurred by chance.

The relationship between the schedule change and achievement in reading is also positive, although the increase was smaller. We found scoring proficient or advanced changed from about 66% to about 69%. But in the results for reading, we could not reject the possibility that they occurred by chance.

Overall, we found no evidence that switching to a four‐day week harms student performance.

These results naturally led to speculation on the mechanisms that drove the results. Could teachers be using alternative instruction methods that enhance learning?

Maybe students on a four-day schedule miss fewer days of school; a number of prior studies have pointed to attendance being a factor in achievement. Or, is it that teachers miss fewer days of school on the alternative schedule?

We did not have enough information in our data to really examine the different possible ways in which the schedule change could improve academic outcomes. Incomplete data on attendance suggested that attendance improved when the schedule was shortened to four days.

But more work would be required on this issue. We also don’t know what is the impact of a four-day week on high schoolers, or how teachers manage this change.

Overall, we believe that the evidence that we found is an important one and should be part of the conversation on education policy.