<![CDATA[Purpose: This study investigates how variations in teachers’ Pedagogical Content Knowledge (PCK) levels directly influence real-time instructional adaptability when addressing diverse student learning needs in heterogeneous secondary STEM classrooms. Method: A convergent parallel mixed-methods design was implemented with 24 urban secondary science teachers stratified into high, moderate, and low PCK profiles. Data were gathered through baseline PCK rubric assessments, 72 observed 50-minute teaching sessions across a 12-week academic term, and post-lesson video-stimulated recall interviews, analyzed via one-way ANOVA and qualitative PCK mapping in NVivo. Findings: Quantitative results revealed statistically significant differences in real-time adaptive behaviors across profile groups (), with high-PCK teachers demonstrating markedly higher adaptive frequency () compared to their low-PCK peers (). Qualitative mapping showed high-PCK teachers dynamically integrated diagnostic student knowledge with spontaneous scaffolding, whereas low-PCK teachers defaulted to rigid lesson scripts. Practical implications: The findings demonstrate that teacher preparation and professional development must transition from generic instructional strategies to topic-specific PCK mapping, enabling educators to reduce real-time cognitive load and implement effective differentiated instruction. Originality/value: This study provides novel empirical evidence illustrating the exact mechanisms through which enacted PCK map networks drive real-time pedagogical flexibility, offering an operational framework for adaptive teacher expertise in diverse learning environments.]]>
