Classroom Management (CM) comprises broad knowledge and skills of teachers. Since CM has been only given little proportion in teacher education, knowledge about the relevance and usefulness of CM contents (CMC) is important. We want to contribute to the knowledge about relevant CMC with four studies. These studies explore the following research questions: Which CMC are needed? What is possible? Are CMC useful for teaching at school? All studies are carried out with the participation of teacher students. In Study 1, we explore the baseline of Classroom Management Knowledge (CMK) of teacher students to deal with challenging situations (N = 158). Study 2, we explore the CMK baseline of teacher students and examines whether CMK which is acquired in a classical seminar can lead to an increase in CMK (N = 17; T1, T2). In Study 3, CMK is validated: How does it affect the practical knowledge of teacher students (N = 58; T1, T2) when facing challenging situations? Finally, we examine the question of Study 4 that asks whether CMK in the classroom can be converted into skills at school (N = 13). The results show that a significant increase in CMK is acquired through a seminar; but the acquired knowledge is very unlikely to be transferred without an intense, long lasting and supportive training of skills. The relevance of these findings is critically related to teacher education.