TRANSFORMING ELEMENTARY MATHEMATICS INSTRUCTION IN REMOTE INDONESIA:A COMPARATIVE EFFECTIVENESS STUDY OF GASING METHOD PROFESSIONAL DEVELOPMENT ACROSS COASTAL AND HIGHLAND REGIONS

Disparities in elementary teachers’ mathematical competence remain a challenge to educational equity in geographically isolated regions of Indonesia. This study aimed to evaluate the effectiveness of intensive professional development using the GASING (Gampang, Asyik, dan Menyenangkan) method in improving teachers’ mathematical pedagogical knowledge across contrasting geographical settings. A quasi-experimental pretest–posttest design without a control group involved 80 elementary teachers, comprising 32 from the Sangihe Islands and 48 from the Jayawijaya Highlands. The intervention lasted 2–3 weeks and covered five arithmetic competency domains. Data were analyzed using descriptive statistics, t-tests, and Cohen’s d effect sizes. The results revealed a significant baseline disparity between Sangihe (57.38) and Jayawijaya (16.33; p < .001). Following training, mean scores increased to 98.81 and 82.63, respectively. Jayawijaya teachers achieved a greater absolute gain of 66.29 points, compared with 41.44 points in Sangihe. These findings indicate the potential of GASING-based professional development to strengthen teachers’ competence in resource-constrained settings. Nevertheless, the remaining post-intervention gap highlights the need for sustained mentoring and context-responsive professional learning to support long-term improvements in mathematics instruction and educational equity. ABSTRAK Kesenjangan kompetensi matematis guru sekolah dasar di wilayah terpencil menjadi tantangan bagi pemerataan kualitas pendidikan di Indonesia. Penelitian ini bertujuan mengevaluasi efektivitas pelatihan intensif metode GASING (Gampang, Asyik, dan Menyenangkan) dalam meningkatkan pengetahuan pedagogis matematis guru pada konteks geografis yang berbeda. Penelitian menggunakan desain kuasi-eksperimental pretest–posttest tanpa kelompok kontrol, melibatkan 80 guru sekolah dasar, terdiri atas 32 guru dari Kepulauan Sangihe dan 48 guru dari Pegunungan Jayawijaya. Pelatihan berlangsung selama 2–3 minggu dengan materi lima domain aritmetika. Data dianalisis menggunakan statistik deskriptif, uji-t, dan ukuran efek Cohen’s d. Hasil menunjukkan perbedaan kompetensi awal yang signifikan antara Sangihe (57,38) dan Jayawijaya (16,33; p < 0,001). Setelah pelatihan, skor rata-rata meningkat menjadi 98,81 dan 82,63. Jayawijaya mencatat peningkatan absolut lebih besar, yakni 66,29 poin, dibandingkan Sangihe sebesar 41,44 poin. Temuan ini menunjukkan potensi pelatihan GASING untuk memperkuat kompetensi guru di wilayah dengan keterbatasan sumber daya. Namun, kesenjangan pascapelatihan menegaskan perlunya pendampingan berkelanjutan dan pengembangan profesional yang responsif terhadap konteks lokal