<![CDATA[Purpose of the study: This study aimed to determine and quantify the differences in collaborative practice and professional communication between graduate and Non-graduate teacher professional education elementary school teachers, and to identify the indicators that most strongly differentiate the two groups. Methodology: An ex post facto causal-comparative design was applied to 120 elementary school teachers (80 Graduate teacher professional education and 40 Non-teacher professional education) selected through purposive sampling in one regency of East Java, Indonesia. Data were collected with a validated 40-item five-point Likert instrument and analyzed using SPSS Version 26 through descriptive statistics, the Shapiro-Wilk test, Levene's test, independent samples t-tests, and Cohen's d. Main Findings: Statistically significant differences favored PPG-alumni in collaborative practice (M = 3.62 vs 3.08; t(118) = 5.84, p < 0.001, d = 1.13) and professional communication (M = 3.71 vs 3.18; t(118) = 6.07, p < 0.001, d = 1.18). All ten indicators reached significance with large effects, and joint lesson-plan development and school interaction intensity recorded the widest between-group gaps. Novelty/Originality of this study: This study provides the first effect-size-based comparative evidence of teacher professional education outcomes on the social-relational competencies of Indonesian elementary school teachers, offering a per-indicator diagnostic framework that advances Professional Learning Community theory in an under-represented education system and informs evidence-driven professional development policy. Implications: the findings provide an empirical basis for prioritizing the expansion of in-service teacher professional education and for designing school-level professional development that targets collaborative lesson planning and school interaction intensity.]]>
