For three years, I taught in a school that utilized the 4-day school week. In our division it was titled the “Plan For Protecting Classroom Instruction” or PPCI.
I now teach in a school under the traditional 5 day format. While it is to lengthy to explain everything in a post about the 4-day model, I can now direct you to some current research that was recently done in our division.
Since school divisions were amalgamated in 2006, our division inherited schools on both the 4 and 5 day models. The division contracted SELU to collect data on both models with a great amount of information documented. The report can be found here and it is a public document.
Many people have asked me which model I prefer. Basically, both are fine. I am a supporter of the 4 day model but have found some elements have eroded over the last few years, which did not happen before. Eg. teams leaving during school time, students on field trips on days other than Fridays (designated day for PD, student events, etc)
Sometimes this year our board will make a decision about our calendar system, that is, stand pat or all go 4 day or all 5 day. Either way a lot of discussion will take place in the coming months.
P.S. My fellow blogger at ThePrincipalsPage.com probably thought I forgot about him and this topic. Hopefully, this post can suffice for a guest posting or I can try to summarize some thoughts at a later date. I think you will find this research helpful.