“…There has been much research in the Netherlands on inequality of educational opportunity (IEO) for pupils of different socioeconomic backgrounds. 1 Beginning with the seminal work of van Heek (1968), the focus of this research has mostly been on the transition that pupils face at age 12, the transition from primary to secondary education, with an overall conclusion that IEO in the Netherlands has decreased only slightly in recent decades (e.g., Bakker, Dronkers, andSchijf, 1982, 1986;Bakker and Cremers, 1994;Bakker and Schouten, 1991;De Graaf and Ganzeboom, 1993;De Jong, Dronkers, and Saris, 1982;Dronkers, 1983Dronkers, , 1993Kloosterman et al, 2009;Peschar, Ten Vergert, and Popping, 1986;Sieben, Huinink, and de Graaf, 2001;Tieben, de Graaf, and de Graaf, 2010;Vrooman and Dronkers, 1986;Willemse, 1987). However, over a longer period, the Netherlands underwent a "process of opening-up and equalization" (Blossfeld and Shavit, 1993:18).…”