School districts nationwide are rapidly adopting 4-day school weeks as they seek to cut costs and fill teacher vacancies by dangling 3-day weekends — despite research showing meaningful learning losses that result.

Why it matters: Less classroom time correlates directly with progressively lower test scores and academic achievement, studies of the 4-day school week ("4dsw") have found.

Driving the news: Nationally, 850 school districts — representing thousands of individual schools — have dropped the 5th day of instruction, up from 650 districts in 2019.

• That's according to yet-to-be-published data compiled by the Four-Day School Week Policy Group at Oregon State University and shared with Axios.

Four-day school weeks are most popular with rural, Western districts, though the trend — which gained steam during the COVID-19 pandemic — is also catching on in metropolitan areas.

• Almost 60 Texas school districts have made the switch or approved it for the 2023-2024 academic year, along with nearly a quarter of those in Missouri.
• Suburban districts in metropolitan Denver, Independence, Missouri, suburban Phoenix and metropolitan San Antonio are now taking the plunge.

How it works: Most schools that adopt the 4-day week are closed on Fridays, but some shut on Mondays.

• School days are longer on the other four days, to compensate for some of the lost hours.
• Some schools offer day care or activities on the remaining weekday that school is closed — for which parents usually have to pay.

The pluses include less burnout and more family time for students and teachers — plus less bullying, per one study — while minuses include mounting evidence that kids in 4dsw programs fall behind their peers.

• One 12-state study, led by Paul Thompson, an economics professor at Oregon State University and leading scholar of 4dsw policies, found "reductions in both math and English/language arts achievement" in districts that adopted the 4-day schedule.
• Another found lower math scores in kids who attend 4-day programs, plus higher absenteeism and lower on-time graduation rates.

A RAND Corp. study found "only weak support for the three main reasons that districts typically adopt the 4dsw: saving money, reducing student absences, and attracting and retaining teachers."

• There's also a "contagion" effect: Some districts adopt a 4-day-a-week schedule to poach teachers from nearby school systems that already have the policy, in a death spiral that undercuts the whole market.

What they're saying: "What the research generally shows is that this is a net negative for student achievement, mostly in scho0ls that see a big drop in instructional time as a result," Thompson says.

Zoom out: The 4-day school week "unambiguously hurts student achievement over time," Christopher Doss, a RAND policy researcher, tells Axios.

• He and a colleague, Andrea Phillips, studied outcomes in six states (Colorado, Idaho, Missouri, New Mexico, Oklahoma and South Dakota) and found that "students in 4-day school week districts fell behind a little every year."
• After eight years, the damage to student achievement would equal the learning loss caused by the pandemic, they estimated.
• Moreover, "we didn't really find that students were engaging in hobbies or extracurricular activities" during their extra time away from school, Phillips tells Axios.

The big picture: Traditionally, states have required schools to meet a minimum number of instructional days per year. But about half of states have switched to requiring a minimum number of instructional hours — giving rise to the 4-day school week.

• The change came first in poorer, rural districts that were primarily looking to save money — and were located in communities where extended families or neighbors tended to be available for child care.
• But since the pandemic, "it's been a wholesale shift, where all schools that are considering it nowadays are doing so for teacher retention," Thompson says.

Meanwhile: Momentum for 4-day workweeks has also been building in the corporate world.

• Benefits include better work-life balance and reduced stress — but good luck trying to get your company to go for it.

The bottom line: Despite the popularity of 4-day school weeks in places that have tried them, "in the long run, the benefits may not outweigh the drawbacks — both in slowing learning and by papering over the deeper issues schools and teachers face," the RAND researchers conclude.