Hundreds of school districts across the United States have adopted a four-day week to save money and help attract new teachers and the idea is spreading.

An estimated 560 districts in 25 states now allow at least some of their schools to switch to a Monday through Thursday schedule, according to the National Conference of State Legislators.

Four states – Colorado, Montana, Oklahoma and Oregon – are leading the trend, which has been in place in some rural districts for decades.

In Texas, only the Olfen Independent School District outside San Angelo has made the transition. It's one of the smallest districts in the state.

But in other states, the idea is catching on in larger districts. Public schools in Denver will begin a four-day week in the fall.

To comply with state laws, most schools make up for the fifth day by adding extra time to the remaining four days.

The idea is popular among teachers and appears to improve attendance rates.

Critics point out the change can be tough on lower-income parents, who may have trouble paying for childcare on the day their kids no longer have class.

Also, low-income students in many districts rely on public schools for almost half their meals — breakfasts and lunches during the week.

Paul T. Hill, a research professor at the University of Washington Bothell who founded the Center on Reinventing Public Education, has argued that while some adults like the new schedule, this “troubling development” could end up hurting rural students.

“The idea has proved contagious because adults like it: Teachers have more free time, and stay-at-home parents like the convenience of taking kids to doctors and doing errands on Friday,” Hill co-wrote in a piece published on the Brown Center Chalkboard blog in 2017. “But, in an environment where young rural adults already suffer from isolation and low economic opportunity, the shorter school week could exacerbate their problems.”

While four-day weeks help cut costs, the amount saved is relatively small.

A 2011 report from the Education Commission of the States examined six school districts and found that switching to a four-day schedule helped them shave their budgets by 0.4 percent to 2.5 percent.