In the first of two talks he gave during his stay in Bamberg Jaap Dronkers discussed the issue of "The effects of educational systems, school-composition, levels of curricula, parental background and imigrants´ origins on achievement of 15-years old pupils." In the presented study he investigates the so far neglected role of schools in the relation social origin and school achievement in different education systems.  In his second talk on "Effects of School’s Share of Single-Parent Families on Educational Performance in a Cross-Comparative Perspective" Jaap Dronkers showed that especially the educational performance of single-mother families is affected by the share of single-parent-families at school.