The assessment of the quality of inclusive schools is an instrument for evaluating five quality levels of inclusive school development and was derived on the basis of the more comprehensive instrument for the external rating of schools the "Quality scale of inclusive school development" (QU!S). The QU!S was developed by Heimlich, Wilfert, Ostertag and Gebhardt (2018) and used in research (Heimlich, Kahlert, Lelgemann, & Fischer 2016). It is based on an ecological multi-level model of inclusive school development (Heimlich, 2003; 2019). The implementation of an inclusive education system is one of the central demands of the UN-Convention on the Rights of Persons with Disabilities 2009. Accordingly, quality of schools must also be measured by the degree of implementation of inclusion. Data-supported feedback loops are helpful to identify the current status of implementation as well as the progress of implementation and the identification of possible problem areas. QU!S sees itself as an instrument which can be used by external consultants, to enter into a dialogue between all those involved in the development of the school. This includes the learners, the teachers, the school management, the parents and other participants. The QU!S-S, on the other hand, is more strongly understood as an instrument of school self-evaluation. This way, a multi-perspective, i.e. objective, picture of the status of implementation and possible focus points can be obtained.