"It doesn't seem to negatively impact achievement, and in some communities they see a slight bump up," said Donis-Keller. She attributes that slight jump to increased student attendance and a greater focus on academics.
In Custer, "our scores went up a little bit," said Creal. "We don't think there's any student achievement increase that we can attribute to a four-day school week but we do know it didn't go down."
Andrea Beesley, senior director of Mid-Continent Research for Education and Learning, a research and consulting nonprofit based in Denver, says there are concerns that plague both parents and communities switching to four-day weeks.
"Depending on the setting, there's a lot of different things that people worry about. Communities worry about what kids are doing when there's no school. They wonder if the kids will get into trouble," Beesley said. "Sometimes parents are worried about childcare. Some people worry about how to keep young students engaged and energized when they have a longer day."
Heather Bradshaw, a single mother with a son in the fourth grade in Peach County, Ga., worries children aren't getting enough time with teachers. Last year, her son's district switched to four days.
"I don't feel like they're having the necessary time in the classroom," said Bradshaw. "The schedule has slowed him down."
Other parents in Peach County prefer the shorter week and say they don't mind finding child care for their kids once a week.
"It makes the children's weekend a little better, so they get more rest," said LaKeisha Johnson, who sends her fourth-grade daughter to the Boys & Girls Club on Mondays, when school is out.
Larger Districts More Complicated
Still, for urban districts, like Broward County, Fla., switching to a four day week is too big a task. The county – with 30 cities and nearly a quarter of a million students — considered a shortened schedule last year.
Superintendent James Notter says the topic didn't even get past the discussion phase. "It didn't get too much out of the think tank," he told ABCNews.com. "We thought 'Well, what are the students going to do on Fridays? If organizations like the YMCA pitch in, who's going to pay for those services?'" So instead of shortening the week, the district consolidated office space and cut down on the administration's budget.
In New Mexico, the state legislature restricts the four-day week to districts with fewer than 1,000 students.
"The logic was that in larger districts, you typically had more families with both parents working," said Jack McCoy, deputy director of learning services at the New Mexico Department of Education. "The options for child care on that fifth day were fewer. In your rural districts, it was more likely that the child would be working at home with their parents on a farm or ranch."
In such districts, the benefits are clear.
"There are some savings. Some see between two and nine percent savings, and those monies can be redirected to instructions," Donis-Keller said. "Some studies show they've been able to save teaching positions through the four-day school week. And teacher absenteeism has also decreased."
For the Custer school district, it appears that after 15 years, the four-day school week is here to stay. "There's been no discussion about getting rid of it," says Creal. "The four-day week in this community has become a way of life."
ABCNews.com contributor Vanessa de la Vina is a member of the University of Florida at Gainesville ABC News on Campus bureau.