Number of books at home and student achievement: new insights from two assessment methods and their interplay with the home literacy environment

Considering the widespread use of the books-at-home index in empirical educational and social research, the goal of the present study is twofold: First, by considering two common variants of the books-at-home index (i.e., number of books for adults and number of books for children) and their relations to the home literacy environment (HLE), we aim to provide further insight into the mechanisms underlying the relation between the number of books and student achievement. Second, the use of two different assessment methods of the number of books (i.e., open-ended questions and photos of the number of books) allows for an initial evaluation of the reliability and validity of the use of questions. Analyses are based on cross-sectional data of 332 parents of elementary school students from Grades 1, 3, and 5 who participated in a web survey in Spain. Multiple linear regression models revealed that, when assessed via open-ended questions, the number of children’s books – but not the number of books for adults – contributed to explaining grades in Spanish and math beyond child gender and parental education. The number of children’s books was also a significant predictor of the HLE, which was unrelated to students’ grades. Comparing results of the two assessment methods revealed high correlations among the number of books collected through open-ended questions vs. photos and a much higher response rate for the questions. Results point to the use of (open-ended) questions as a viable approach for collecting the number of books in empirical research.