The relationship between family structure and performance in PISA was examined in the volume devoted to equity in PISA 2012. The equity framework in PISA 2015 focuses on the concentration of disadvantage and its association with students' access to educational resources, on differences in opportunity to learn, and on grade repetition and tracking. This chapter looks at how these mediating factors interact with students' socio-economic status, Chapter 7 examines how they affect students with and without an immigrant background.