I don't know about research on extended school days, but being from
Colorado, I do know that there are school districts that follow this
schedule for the important purpose of skiing on Fridays. They may or may
not have had to argue their cases with research, and/or they may be able to
give feedback on pros and cons, snow conditions, etc. As far as I know,
school districts in Winter Park and Brekenridge, CO, follow this model.
Kevin
Kevin Leander
Doctoral Student, Curriculum & Instruction
(217) 333-6604
http://lrs.ed.uiuc.edu/students/k-leand/homepage/index.html