Gov. Josh Shapiro signed legislation in December which amended the Pennsylvania School Code, allowing districts to choose between 180 school days and hourly instruction requirements: 900 for elementary students and 990 for secondary students.

Four-day school weeks with extended hours Monday through Thursday or Tuesday through Friday would meet the hourly instructional requirements.

“This is an important piece of legislation, because every school district and especially those that are in the vo-tech area, they may have different needs than deal with the number of days that students need to go and the number of hours that students need to go,” said state Rep. Aaron Bernstine, as quoted by the Associated Press.

Supporters of the legislation hold that the amendment allows schools to accommodate weather conditions, student apprenticeships, internships, and career and technical education programs, as well as professional development and community events.

It will also let schools track students who learn remotely through hours of instruction, rather than days.

“Making it flexible so that families can have the time to spend with each other would be beneficial, but if we are going to do it for schools, we need to do it for work as well because a lot of parents have 9-to-5s and they have strict schedules,” parent Leta Scott said, as quoted by the Associated Press. “So to be able to accommodate the school schedule being different it would have to be different all the way around so we could actually have that time with our kids.”

Pennsylvania was one of 18 states with a day and hour requirement before Shapiro signed the bill. According to the Associated Press, hundreds of school systems around the country have adopted four-day weeks in recent years, mostly in rural and western parts of the U.S.

Districts cite cost savings and advantages for teacher recruitment, and while surveys show parents approve overall, support wanes among those with younger children.

According to Education Next‘s analysis, students earn lower math and reading scores on standardized tests after their schools switch to a four-day schedule.

U.S. schools with four-day schedules offer an average of 148 school days. The earliest known use of a four-day school week dates back to the 1930s in South Dakota, Education Next said.

The bill can be found here.