ST. PAUL (AP) - 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.

Cassellius says students aren't making adequate academic progress because of the shorter weeks.

The shorter weeks proved popular with families and teachers because of the resulting three-day weekends. They also saved money that was going to transportation costs.

Five districts have been approved for a transitional year and will return to five-day weeks by the 2015-16 school year. Three districts will revert this fall, one voluntarily.  Three others with four-day weeks will come up for renewal in 2015 or 2016.