A shorter school week could not only save money for school districts, but may also lead to improved student achievement, according to a recent study by professors from George State and Montana State universities.

The study focused on Colorado, where more than 30 percent of school districts have moved to a four-day week. Only about 3 percent of the state's students attend those districts, though, as the movement has largely been restricted to rural areas. The authors analyzed test scores on statewide exams for fourth-grade reading and fifth-grade math to gauge the effect of the new schedule.

Controlling for a number of factors, the analysis concluded that the adoption of a four-day week did lead to improved student achievement for schools that switched their schedule during the study period. The shorter week is associated with a 7 percent increase in fifth-grade math scores, and a 3 percent increase in fourth-grade reading scores. The study found that fifth-grade students moving from partially proficient to proficient in math accounted for the largest change. For fourth-grade reading, the most significant changes consisted of students moving out of the lowest-achieving level or moving into the highest-achieving level.

The authors don't attempt to attribute specific causes to the improvement; however, they pose some hypotheses, such as more focused instruction, improved student attendance and increased morale.

It is noteworthy that, on average, schools with four-day school weeks still score lower than schools with traditional schedules in both grades and subject areas. However, those gaps already existed prior to the new schedule. Schools with four-day weeks also had more students in poverty, which is typically associated with lower test scores.

The four-day school week has largely gained popularity in rural areas, as in Colorado, the study's authors noted. The schedule has been adopted in part in 17 states and is most prevalent in Colorado, New Mexico and Wyoming. Studies in Georgia and Kentucky have demonstrated significant savings for school districts that switched to four-day weeks, according to the authors, but this study represents one of the first efforts to document the impact on student performance.

The full study can be found below.