In America, majority of public schools require five days a week with only two days off. Despite the amount of time students spend in school, they might not be learning as much as you'd think. About 22% of highschoolers were failing post-pandemic. So maybe what we really need is more hours a day in school, rather than more days.
There are many reasons why schools are debating the 4 day a week school week. There might be a lot more pros if school decides on a 4-day school week. The first reason being, from already performed studies. The students who already have 4 day school weeks say having to spend more time in school is worth the Monday off. More time can be spent in each class, making sure students indulge in what they're learning rather than going through the motion of short periods each day. By the time students settle into class and are ready to learn, the bell rings. So having more time to have focused students would be very beneficial in the classroom.
The next reason is flexibility. Having a 4 day school week gives our teachers and administrators a whole weekday for their errands, meetings, appointments, etc. This means teachers will miss less time with their students. Having a substitute is sometimes detrimental to students learning. Especially if the same class has an absent teacher often. Giving our teachers an extra day means teachers will spend more time helping those students who need it, and less time without a teacher.
Lastly, mental health. (I'' add later)