Heterogeneity in the classroom and the appropriate handling of individual student prerequisites present a central teaching challenge for educators. This book addresses teacher interventions in mathematical modeling as a specific aspect of dealing with heterogeneity in subject teaching. The core of the work is the description of an empirical study that exploratively examined teacher interventions during student-centered support of mathematical modeling processes. Both qualitative case analyses and frequency evaluations of the observed teacher interventions demonstrate that intervening during student-centered learning phases is a complex endeavor.