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.