The paper focuses on a comparison of linguistic performance of migrant and non-migrant students. One assumption is that school achievement might be less dependent on general (everyday) language competence (“basic interpersonal language skills”) than on academic language competence (“cognitive academic language proficiency”). In the research project “Full-time schooling and the integration of migrants”, approximately 1500 5thgraders were tested with the instrument “Fall into the Bed of tulips”, which tests productive written language skills in German and the heritage language (Turkish/Russian). The analysis provides information about narration competence, general-language and academic language competence. The test was constructed with reference to the differentiation of the two respective registers. The evaluation of the results has shown that student’s use of the academic register fell short of expectations. This might be due to methodological constraints of the instrument used for elicitation. Thus, an additional impulse was developed by which the use of the academic register should be better evoked. The instrument and pretest-results will be presented in the contribution.