Matilda - Learning to Teach Mathematics Inclusively" is an interdisciplinary research project funded by the Federal Ministry of Education and Research to qualify educational specialists for inclusive education. The project is led by Prof. Dr. Susanne Prediger (Professor of Basic Mathematics Didactics at the Institute for Research and Development of Mathematics Education) and Prof. Dr. Jan Kuhl (Professor of Instructional Development Research with a focus on inclusion). The interdisciplinary, mathematics didactics/special education professionalisation and research project addresses special needs and mainstream teachers at lower secondary level in multiprofessional tandems. The cross-project interlocking of subject didactic and special needs education elements is taken into account in a four-month professionalisation project, which was developed with the inclusion of relevant design principles for teacher training. For this purpose, a series of lessons on the topic of percentages was designed for inclusive mathematical learning in Year 7. Regular and remedial teachers are to test and systematically reflect on the exemplary inclusive lesson unit on percentages. The aim of the Matilda research project is to gain insights into professionalisation and teaching processes through the development and testing of this evidence-based qualification concept and to evaluate these using a mixed-methods design. The overarching research question of the project aims to examine effects of this specific training on the level of teachers as well as on the level of students with the help of process and effectiveness analyses. Thus, four research questions at teacher and learner level are at the centre of the research interest:

•     What effectiveness do the material- and further training-based qualification concepts show for the knowledge and attitude changes of regular and support teachers?
•     Which individual professionalisation processes can be reconstructed among the teachers?
•     What is the effectiveness of the material- and in-service training-based qualification concepts for the mathematics performance of learners in all ability profiles?
•     Which learning processes can the qualified teachers initiate for learners with and without special educational needs?
•     How can individual and joint learning succeed?