Aended Tuesday when the . Now, teachers in Oklahoma could be the next to go on strike over low wages.
Talk of a walkout comes after some schools switched to a four-day school week, with slightly longer hours each day, to try to make up for low pay. Two-hundred and ten of the state's schools -- in 91 of the state's 512 school districts -- operate on a four-day schedule.
While it appears to be popular with some teachers, others express concern about what the schedule will mean for children's education and the lives of busy parents.
How does a four-day school week work, and what are some of the pros and cons of the modified schedule?
One Oklahoma school that moved to a shortened schedule in 2016 to cut costs noticed that while it didn't save much, more experienced teachers applied for jobs there, reports CBS News' Omar Villafranca.
In another case, Bob Gragg, the superintendent of White Rock schools in Oklahoma, said one teacher he knows discussed the importance of the schedule when deciding which job offer to accept.
"I did have one teacher that recently told me ... that she had choices of more than one job offer in our area, and she chose White Rock because she was intrigued" and wanted to try the schedule, he said.
Bridge Creek Superintendent David Morrow said his district cut down the school week to recruit teachers in 2016 amid a statewide teacher shortage due to low pay. Afterward, he noticed a difference.
"When we were on the five-day school week, I had three openings at our elementary school and had four applicants.... Same three openings now and you have 15 to 20 applicants," Morrow said.
Jalaine Watham, who teaches second grade at Bridge Creek Public School outside Oklahoma City, said she loves working a shortened week.
"It has allowed that weekend time with my family, but I also really truly feel like it has made me a better teacher by being purposeful and looking at time management," she said.
Parents and children
The modified schedule could, however, pose challenges for parents who work five days a week. If their children can't go to school on Fridays, child care becomes a question.
Gragg, of White Rock schools, indicated that in his community it hasn't really been a problem.
"So far, the parents have been over 90 percent in favor of the four-day week, which surprised us a little bit," he said. "I think there are enough grandparents and relatives in our community that that's not an issue on Friday."
Gragg also said the schedule works with the local culture.
"We have a lot of parents that work four days a week," he said. The community is near Tinker Air Force Base, and some of the work schedules at plants in the area operate on a four-day work week. "So having a four-day work week as a local community culture -- that seems to fit very well in White Rock," he said.
Oklahoma's public school system requires students to attend at least 180 days or 1,080 hours of school per year. Shorter weeks mean longer days, which can range from 40 minutes to an hour more in some cases.
The state superintendent of instruction, Joy Hofmeister, worries about the long-term impact on students.
"We are losing valuable time to sustain momentum and grow," Hofmeister said. "Just extending more minutes to the day is not actually the same as having more days in the calendar year."
Gragg, however, sees opportunity.
"I see some great value in a shorter week -- more time on task. There are opportunities for our students to do things in a longer day that they might not have time for in a traditional six-hour day," he said.
CBSN anchor Anne-Marie Green asked Gragg about the risks of the schedule possibly resulting in something similar to the "summer slide."
"The first thing I thought about when I read about this four-day week was something akin to the 'summer slide' -- that as children stay away from school, they stay away from school long enough, they start to slip back a little," Green said. "And this is three days off, away from your homework and teachers."
But Gragg said he hasn't seen this kind of impact.
"This is our second year to do the four-day week this time around," he said, noting that White Rock schools had also done a four-day schedule for a period in the late 1990s and early 2000s, "and they actually did not see a slide backwards in academics, so that would be a concern if we began to see that."
"Some of the studies that we've read have not indicated a drop-off, which is really kind of amazing," he added. "But we are concerned with that and will continue to watch that issue, because if it begins to impact academics in the long run, then we're going to certainly rethink and have a re-conversation with our community. But so far, we don't see that happening."
He also said attendance has been "a little better" with the four-day week.