“What a difference a day makes: the argument for a four-day school week”

In this article from The Guardian Lucy Rycroft-Smith introduces the idea of a shorter school week, and references a recent study in Colorado where shorter school weeks, with longer days, were introduced.
I can’t see this happening any time soon, certainly not in Australia, but it could be an interesting discussion to have. Obviously there would be problems around care for children whose parents work a full 5-day week – as Rycroft-Smith mentions – but in terms of both teacher and student workload, and student engagement, perhaps there is some merit in discussing how the traditional school framework could be adjusted so the time is used more effectively.
The article seems to be mainly considering the possibility for primary aged students, however I think the discussion could be had for all ages. In many secondary schools, senior students often have an afternoon off one day a week, and although this is usually introduced for the purpose of study time, often students use the time to work, or spend time with friends, and therefore it’s not really very effective in terms of the intended purpose. However, perhaps senior students could be considered old enough to decide for themselves how they spend their time? Certainly less students in certain blocks of the week provides time for teachers to plan, collaborate, grade, and complete other tasks that often happen outside school hours.
I would certainly be open to consider how we could structure time in schools more effectively, although I think it would be a messy discussion when you consider how many different stakeholders would be involved; education departments, parents, students, teachers, unions etc.