What's about the books? Social background of students and educational opportunities from the perspective of international large-scale surveys

International large-scale assessments are designed to identify characteristics of educational systems which only can be identified by comparing different systems. The comparison is necessary once within a country characteristic does not show any variance or if normative standards are not available to that a characteristic could be related. Special attention in this context is given to the relation of social background of students and their success in school. As theoretical framework - especially in European countries - the work from Pierre Bourdieu is often used in which social, cultural and economic capitals are distinguished. In international large-scale surveys the question to students and/or their parents about the books at home is tradition since some decades. This indicator is an easy to survey and robust indicator for cultural and economic capital. Taken into account the accelerating availability of digital media in the households the question rises, if the question on the books at home is still appropriate. This questions lies in the focus of the article. Answers are sought by analyzing background information and form the German data of the Progress in International Reading Literacy Study (PIRLS) in the four cycles from 2001 to 2016. By using models of probabilistic item response theory the characteristics of the indicators available - which address the cultural and economic background of the students - are investigated over a 15 year period. The results show that the information about the books at home is still a robust and stable indicator for the description of the educational background of the students.