Here are some links to information on the four-day school week:
This is a 2009 research brief done by the University of Southern Maine:
University of Maine research brief
Here is a link to a document published by the Colorado Department of Education on the 4-day week in Colorado:
http://www.eric.ed.gov/PDFS/ED429344.pdf
Here is a link to a research paper From the University of Arkansas:
http://edle.uark.edu/Four-Day_School_Week_NCPEA_2010_2ndEd.pdf
You can find many other research briefs, but these are the most recent and well respected.
