The main objective of this study as determined by the funding public authorities (City of Ghent, Education Department) was to investigate whether the local project ‘Home Language in Education’ (2008-2013) increased the opportunities for school success (achievement and well-being) among the pupils, and which features in the learning and teaching environment of the four participating elementary schools could have contributed to this. The research design is longitudinal, quasi-experimental (control group), pretest-posttest, and multi-method (qualitative/quantitative). In addition to detecting effects among pupils, process-related changes were examined with teachers, schools and parents. Pupil effects were merely demonstrated in the domain of well-being, however only partially detectable in the quantitative measurement. Effects on Dutch language proficiency (reading comprehension) were not ascertained for the two project aims (Aim A: valorising and using home languages in mainstream classes; Aim B: literacy instruction in first language Turkish). The largest change among teachers was noticed in their attitudes and notions concerning multilingualism, which was expressed in an increased awareness of linguistic diversity. Teachers’ actions showed a positive development to a certain degree, notably in primary school and at the start of the project. Teachers themselves assessed the project’s impact on their actions as moderately positive. Parents’ beliefs on the role of home languages at school did not change significantly during the implementation of the project; they tended to cling to a monolingual approach to education (= submersion in Dutch language; only-Dutch school policy), which mirrors the dominant ideology in society. ; Aan de hand van dit onderzoek wilde de opdrachtgever (Departement Onderwijs en Opvoeding van de Stad Gent) te weten komen of het plaatselijke project ‘Thuistaal in onderwijs’ (2008-2013) de kansen vergrootte op schoolsucces (prestaties en welbevinden) bij de leerlingen en welke kenmerken in de ...