INSIDE I provides data for the quantitative analysis of the starting points, retention situations and careers of inclusive pupils. INSIDE I surveyed and tested approximately 4.600 students, 13% of whom had SPF, at 280 schools. This unique longitudinal study generated evidence-based knowledge about inclusive learning in lower secondary schools. In addition, a data basis was created that also serves as a starting point for the second funding phase INSIDE II. This supports the project of describing transitions after lower secondary school and identifying various conditions for successful transitions depending on different school conditions.