ST. PAUL — A money-saving experiment by a handful of Minnesota school districts that switched to four-day school weeks is winding down because of academic performance concerns.

Education Commissioner Brenda Cassellius has told seven of the 11 rural districts with four-day weeks to return to normal schedules, according to reports. An eighth district, North Branch, is reverting voluntarily this fall.

Students aren’t making adequate academic progress because of the shorter weeks, Cassellius said.

The shorter weeks proved popular with families and teachers because of the resulting three-day weekends, but the state Department of Education concluded that test scores in those districts weren’t improving.

“It’s an example of how Minnesotans are creative when faced with challenges,” department spokesman Josh Collins said. “But I think what it comes down to is what’s in the best interest of students and learning, and in that regard we’re just not seeing that the four-day week was something that provided a benefit to children.”

Districts given a one-year transitional period to return to five-day weeks include the sprawling Lake Superior school district in northeastern Minnesota, which switched to a four-day week in 2011. Busing students from remote areas into Silver Bay and Two Harbors only four days a week saved the district $180,000 a year, Superintendent Bill Crandall said.

“Some of our students are on the bus one way for an hour and 45 minutes,” he said.

Crandall said the four-day schedule also cut energy and food service costs, bringing the total savings to $225,000 a year.

The state told five districts to return to five-day weeks by the 2015-16 school year. They are Belgrade-Brooten-Elrosa, Lake Superior, Ogilvie, Maynard-Clara City-Raymond and Pelican Rapids. Three districts will revert this fall: Clearbrook-Gonvick, Onamia and North Branch.

Three others with four-day weeks that will come up for renewal in 2015 or 2016 are Blackduck, Warroad and Atwater-Cosmos-Grove City.