The goal of MITHOS is to provide mixed reality (MR) supported, sustainable social skills acquisition for the classroom. MITHOS provides realistic socio-emotional training opportunities in which prospective and practicing teachers can better prepare for the challenges regarding conflict and heterogeneous groups in the classroom. The consortium is realizing this through an immersive MR environment. This integrates a human-controlled avatar and multiple virtual student agents that act differently using artificial intelligence. By means of sensor technology, a precise real-time recording of social signals from the face, body and speech of the teachers is possible. In this way, the teachers train their perception of their own needs and their ability to empathize, as well as their ability to adopt perspectives and regulate conflicts in heterogeneous learning groups.