Gothenburg, the second largest city of Sweden, has a rather high proportion of school segregation (index 0.26), which is above national level. Differences in school quality have been shown due to school segregation. One factor is related to effects from peer relationships (Gustafsson, 2006). Previous obstacles in measuring peer effects have now decreased (see for example Hoxby, 2000; Boozer & Cacciola, 2001; Gustafsson, 2003; Zimmerman, 2003).