I'd be interested to know more about the control measures in place on these studies.  It seems to me that schools that are "going green" are more likely to be in more affluent areas while "un-green schools" would be in less desirable areas.  A school district that is fighting for text book funding isn't going to be too focused on environmental issues.  To answer your question though I think the answer is yes, going green could in theory increase a school's test scores.  I suppose it would also have to do with how un-green the school was before the transition.  You could easily test the opposite of this though.  I imagine that if I sat next to a student as they tested and blew cigarette smoke in his face his scores would decrease.