Librarian staffing and reading scores study

In a longitudinal study, researchers found that schools that either maintained or gained an endorsed librarian between 2005 and 2011 tended to have more students scoring advanced in reading in 2011 and to have increased their performance more than schools that either lost their
librarians or never had one.
Lance, K.,& Hofschire, L. (2012). Change in school librarian staffing linked with change in CSAP reading performance, 2005 to 2011. Denver: LRS.
http://www.lrs.org/documents/closer_look/CO4_2012_Closer_Look_Report.pdf