As yet, no consensual answer has been given to the question of how the native languages of students of migrant background and the lingua franca (German) should be dealt with by the school and in the classroom. The article critically evaluates pertinent research, focusing on the research methods applied, and reaches the conclusion that the competence in native languages apparently does not foster the learning of the lingua franca. As far as school achievement is concerned, competence in the lingua franca seems to be very closely connected with school success. Recently published studies which contain evidence of causal relationships between language competence and school achievement are especially closely examined. Furthermore, an intervention study comparing types of treatments for language learning is discussed and the relevance of broader studies in psychological learning theory to school learning is inquired. Finally the consequences of the findings for school practice and future research are summarized and discussed: ▶ About one third of all students in school age are and will be children of migrant background; their presence will be a constant task of the German schools. ▶ These students come from more than 150 countries and speak close to 200 family languages; the need for a lingua franca is evident. ▶ Until today their school achievement is much worse than that of students without migrant background, the difference being between 2 and 3 school years. ▶ There is a strong co-variation between school achievement and competence in the German language which leads to the recommendation to invest into intense training of the language of the school, without recurrence to the family languages. © Georg Thieme Verlag KG Stuttgart.

German as a second language Migration Family language Lingua franca research methods bilingualism school achievement multilingualism

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