The most recent study (Schubert, F. and Becker, R. 2010. Social inequality of reading literacy, A longitudinal analysis with cross-sectional data of PIRLS 2001and PISA 2000 utilizing the pair wise matching procedure. Research in Social Stratification and Mobility 29:109-133) showed that the home print environment was a strong predictor of reading achievement, even when income, parental education, aspects of schooling, language used at home, and other aspects of the home environment were controlled. The authors concluded that the home print environment was as strong a predictor as socio-economic status (see the references to the other studies below).
What does this mean in the real world? It means that closing or cutting funding to public libraries and slashing school library budgets is counterproductive in the quest to help children grow in reading.
Writing about changes in reading instruction in Milwaukee, Bob Peterson and Stephen Krashen recently wrote:
Research also tells us that the children who do better on tests of reading comprehension are those who have more access to books and who read more. Studies consistently show that better school libraries, those with better collections and with a credentialed librarian are related to higher reading scores. What this means for Milwaukee is that any reading plan has to involve improving school libraries. This is especially important in high-poverty areas, where the school library is often the only source of books for children.Our school system just eliminated Middle School Librarians, replacing them with non-certified staff.
Achterman, D. 2008. Haves, Halves, and Have-Nots: School Libraries and Student Achievement in California. PhD dissertation, University of North Texas. http://digital.library.unt.edu/permalink/meta-dc-9800:1
Krashen, S., Lee, SY, and McQuillan, J. 2010. An analysis of the PIRLS (2006) data: Can the school library reduce the effect of poverty on reading achievement? CSLA Journal, in press. California School Library Association.