Replicating McQuillan’s analysis of 1992 NAEP scores, this study found that access to books in school and public libraries was a significant predictor of 2007 fourth grade NAEP reading scores, as well as the difference between grade 4 and grade 8 2007 NAEP reading scores, suggesting that access is important for improvement after grade 4. Access (school/classroom libraries) was a significant predictor of scores on the PIRLS test, a reading test given to fourth graders in 40 countries.
Krashen, S., Syying, L., & McQuillan, J. (2012). Is the library important? Multivariate studies at the national and international level. , 8(1), 26-36. http://www.sdkrashen.com/content/articles/multivariate_studies.pdf