This study identifies proficiency levels in pre-service physics teachers' pedagogical content knowledge (PCK) and reveals how teacher education can promote transitions into higher proficiency. Teacher education plays a fundamental role in supporting pre-service teachers' PCK development. Proficiency levels are a powerful source when evaluating this PCK development because they characterize what learners are likely to be able to know on a specific level. Previous research has presented a model of proficiency levels in pre-service physics teachers' PCK; however, evidence for the model's validity is still lacking. According to the Refined Consensus Model of PCK, factors such as teachers' content knowledge (CK), their teaching experience, and their beliefs about teaching and learning science promote PCK development. Thus, understanding how and when pre-service physics teachers' CK, teaching experience, and beliefs contribute to their proficiency can bring insights into how teacher education can promote PCK development. To address this issue, N = 427 observations of pre-service physics teachers were analyzed. Utilizing the scale anchoring procedure, four different proficiency levels in pre-service physics teachers' PCK were identified. Analyzing these proficiency levels showed that lower levels can be characterized as remembering content-unspecific knowledge, whereas higher levels encompass content-specific strategies to structure and elaborate lessons. Additionally, logistic regression models revealed that pre-service physics teachers' CK is crucial for an increase in PCK proficiency. However, transitions into higher levels of PCK additionally require teaching experience and adequate beliefs about teaching and learning. Thus, our proficiency levels can be used to bring insights into how proficiency in PCK can be supported during teacher education. For example, teacher education should provide courses focusing on the science curriculum and the assessment of student learning to promote pre-service physics teachers' progression in PCK.
