I think it is worth a try, but I don't expect it to be a good way to improve education. Right now, in my school, the kids attend 7.5 hours for five days, which is 37.5 hours per week. Divide that same time by four and it's nine hours and twenty-two minutes.
I can tell you, most kids are exhausted by last period as it is. At least exhausted of learning, they still have to be yelled at to stop running in the halls on the way out. I try to schedule my special kids for their core classes in the morning, while they're fresh. so they can burn off energy at PE, and relax in Art or whatever.
I think teachers would be exhausted also, with such long days. Exhausted to the point that they would stop functioning well as teachers. Before I taught, my assumption was that a teachers work was how I remembered my teachers: take roll, give a brief lesson, and sit at their desk while the kids worked on worksheets, looking up answers, or doing math problems. It ain't like that at all. Not complaining, I love my job, but at the end of the day, I'm spent.
Still, let them try it and see. We need to think outside the box, if we don't want Asian kids to keep kicking our asses in international testing.