For some time now, features like parents’ country of origin or the family language have been surveyed in addition to citizenship in order to collect more valid data for education planning and educational research. Each of the formed indicators is labelled “migration background”. However, it is clear that the operationalisation used in governments statistics and educational research is not consistent over different studies. The present contribution aims at illustrating this inconsistency with data from the German school statistics. It will be demonstrated which problems stem from the heterogeneity in the definition of “migration background” – especially for the comparability of results from different studies.

Keywords
foreign pupils, migration, migration background, citizenship, citizenship law