I don't know if this is the case in the OK schools, but I've read that in other districts that do this, it's not like they just cut out 7.5 hours of education per kid per day. They absorb those hours into the other days. The savings, as previously noted, come from bussing, breakfasts and lunches, hourly staff, that sort of thing. Kids still attend the same number of hours per week. On the surface it seems like a reasonable solution.
However, the kids who most need the structure of school are now the ones who will suffer. For many students in today's society, school is the one place where they feel safe, structured, supported, loved. It's where they can actually get a meal and where, despite the problems in schools today, they might not feel threatened by authority figures, particularly in the lower grades. There's a movement in education today to practice what's called (if I recall correctly) "trauma-informed education," which is essentially trying to understand where students are coming from and how the stressors they're experiencing in their everyday life affect their ability to achieve in school. It's not handling students with "kid gloves," and it's not saying that everybody is a special little snowflake. It's understanding that when a student goes home and mom and dad are drinking and fighting, and Uncle Joe gets a little too handsy, and you can't sleep at night because of partying that the neighbors are doing, and your brother is in jail, etc. etc. etc., your brain is constantly in a fight or flight response pattern and you are biologically unable to learn. The schools try to develop ways to help bring you down from that level of alertness to allow you the opportunity to be able to learn.
Now when you have students who are in poor, high-stressed communities, what do you think is going to happen with that flight-or-fight response when they're away from school not for two days a week, but for three? What do you think is going to happen when students who have difficulty getting a good meal at home go from getting five guaranteed lunches a day to four? When students who might already be unsupervised for most of the day are suddenly at home and unsupervised for another day a week? When parents who might already struggle to make ends meet suddenly need to find care another day every week for their children?
I understand schools trying this as a way to make ends meet in the face of reduced budgets. The fault here is with the lawmakers for not having the guts or wisdom to say that education is important, that the structure of school is important, that an investment in youth pays dividends for ALL of society for DECADES after those youth graduate school.