Abstract
<p>This sub-study evaluates the effectiveness of an intensive Generative Artificial Intelligence (AI) professional development program in enhancing primary school teachers' AI-based Pedagogical Content Knowledge (AI-PCK) and identifies the specific component that yielded the highest level of improvement. Using a quasi-experimental pretest-posttest design, the study examined a sample of 142 in-service primary school teachers. Data were collected via a researcher-developed questionnaire covering 5 distinct components of AI-PCK and analyzed using paired t-tests and Cohen’s d effect size.The findings confirmed a highly significant overall positive impact of the professional development program on the teachers' total AI-PCK scores (p&lt;0.001), accompanied by an exceptionally large effect size (d=3.71). Learning gain analysis revealed that the fifth component—familiarity with and application of assessment rubrics—experienced the most substantial improvement, achieving the highest learning gain (2.65) and the largest individual effect size (d=4.82). This result implies that in the era of Generative AI, the critical professional development priority for primary school teachers has shifted from content creation tools toward mastering the design of authentic, process-oriented assessment rubrics. This research offers a foundational framework for educational policymakers addressing the challenge of AI authenticity in primary education.</p>