More than 2,100 schools in more than 850 districts across 26 states have made the switch to a four-day week, according to researchers at Oregon State University. Most are rural districts dealing with tight budgets and ongoing struggles to recruit and retain teachers. Now the war in Iran and the resulting surge in oil prices could push even more cash-strapped districts to consider the schedule, even though research suggests it can come at a cost to students.

The fuel crunch has already shortened school weeks overseas. In March, Sri Lanka moved its schools, universities, and government offices to a four-day week, giving everyone Wednesdays off to conserve fuel.

Why four-day school weeks

Educators first turned to four-day school weeks during the Great Depression to save money as the country struggled through the financial crisis, according to University of Oregon professor Sean Grant, director of educational research at the HEDCO Institute.

Grant told Fortune that the current wave has not yet felt the impact of the Iran war and its oil shock. Historically, however, schools start considering alternative schedules during times of financial strain.

Grant said there have been “clear phases” when four-day school weeks gained popularity. After the Great Depression, school districts revisited the idea during the energy crisis of the 1970s, following the 1973 Arab oil embargo and the painful years of stagflation that followed. More recently, Grant said, came “the Great Recession, the housing crisis, and you could consider the current wave now, the fourth sort of post-pandemic.”

Grant’s team found that most schools now use the schedule to recruit more teachers and adjust budgets to elevated inflation and an affordability crisis that has hit institutions as hard as individuals.

Does it work?

Many schools have seen success in recruiting teachers, but saving money is a false promise, according to Paul Thompson, a leading researcher on four-day school weeks and an associate professor of economics at Oregon State University.

“We heard a lot of anecdotal evidence of, like, hey, districts are saving a lot of money from making this switch,” Thompson told Fortune. But the actual savings are much smaller than most people expect.

“Research has shown it doesn’t really have this kind of windfall of savings for school districts. It provides them some financial flexibility, like saving one to 2% of their overall expenditures,” Thompson said.

And for those marginal savings, many studies have found the schedule can hurt student achievement.

The “big takeaway,” Thompson said, is that without a fifth day, and without longer school days to make up the difference, students spend less time in school, which drags down their achievement.

“We looked in Oregon, and we found that weekly time in school was dropping by about three to four hours per week. That translated almost directly to the achievement declines that were found in those districts,” Thompson explained. “And if you look nationally, you see kind of the same thing.”

Still, Thompson notes that a four-day week is not a “one-size-fits-all approach.” For some schools, it has helped retain and recruit teachers while minimizing negative effects on students.

The Martensdale-St. Marys Community School District in Iowa adopted the four-day week for the 2024-25 school year. Before that, its superintendent, William Watson, was strongly opposed to it. “I thought it was crazy,” he told Fortune.

But the rural district kept losing teachers to higher-paying districts closer to Des Moines, Iowa’s largest city, about 20 minutes away. “Three years ago, when I arrived, the previous year, we lost 10 teachers to other districts,” Watson said.

While the district chose the new schedule to keep classrooms staffed, the change brought other benefits, including higher student and staff morale.

Much of that success comes from keeping learning time nearly the same. “In 2023-2024, students in our district attended school for 1,087 hours. In ’24-’25, they went for 1,080 hours, so seven hours less. And then last year they went for 1,084, so three hours less,” Watson explained.

Thompson said these decisions are a give-and-take for schools facing money troubles and teacher shortages, and there are often no perfect options.

“You know they’re always thinking about these kinds of trade-offs, and you know if we have a limited budget, where do we try to cut costs,” Thompson said. “But with financial pressures, there’s never any good outcome.”

It’s a practical decision that seeks to make the best of a bad situation.

“Maybe the four-day school week is showing some detrimental effects to students, but is it any worse than the other options that districts might need to go to to alleviate these financial pressures?” Thompson asks.