Achievement gaps between immigrant and native students indicate failure to assure educational equity in the majority of countries assessed by the Programme for International Student Assessment in 2009 (PISA, 2009). The present article explains disparate achievement results in Europe, first testing the hypothesis of old and new democracies. In further contextualisation of the achievement results, the analysis seeks explanations beyond the common education system explanatory model. Specifically, the article considers results from Croatia, Serbia and Slovenia, highlighting the significance of language distance between native and immigrant students as well as migration regimes as important factors in creating or reducing the achievement gap between native and immigrant students. Evidence has been found that immigrant students score worse in countries with guest labour immigration regimes than in the countries with large scale forced immigration of people of the same ethnic (linguistic) origin.