Аннотация:Abstract In recent years, many studies have researched the impact of teachers' professional knowledge on teaching quality. Those findings are still ambiguous providing unclear evidence for supporting teacher education programs that aim at developing professional knowledge. In this study, we followed a new approach and used a “performance test” to take a closer look at the impact of professional knowledge on teaching quality. We simulated one particular teaching situation in a controlled, standardized setting in which student teachers ( N = 109) enrolled in physics teacher training courses at five German universities had to explain given phenomena to high‐school students. These high‐school students were trained to behave in a standardized way and to ask standardized questions. Videos of these situations were analyzed using an established model of explaining physics. The validity, reliability, and objectivity of these performance tests for explaining physics were examined in previous studies. In this article, we report on the analysis and interpretation of the results of our study concerning the impact of physics content knowledge (CK), pedagogical content knowledge (PCK), and two groups of beliefs (specific aspects of (i) self‐efficacy and (ii) teaching and learning) that mediate the effect of CK and PCK on student teachers' explaining performance. Using path analysis, we can show that student teachers' PCK mediates the influence of their CK on explaining performance in that CK only has a positive influence if PCK has also increased as well. Our findings stress the key role of PCK. For one particular teaching situation, we can show the positive influence of student teachers' CK and their PCK they acquired in academic teacher education on their teaching quality.
