Greening America's Schools: Costs and Benefits http://www.resourcesaver.com/ewebeditpro/items/O59F10148.pdf by Gregory Kats was recently released (date on the report is October 2006). Sponsors of the report include the American Institute of Architects and the U.S. Green Building Council.
An interesting study -- however a caveat has been posted on the Society of Building Science Educators list: the study uses LEED credits to indicate a level of "green" that may not be substantiated with actual tests. [It is generally acknowledged that estimates of energy use prior to building often do not pan out in practice.]
A previous report by Gregory Kats dated December 2005 is on a similar topic: National Review of Green Schools: Costs, Benefits, and Implications for Massachusetts. http://www.cap-e.com/ewebeditpro/items/O59F7707.pdf