<![CDATA[Critical thinking and self-confidence are cognitive and affective competencies elementary students need, yet both remain underdeveloped in Indonesian mathematics classrooms. This study examined the effect of the GASING (Gampang, Asyik, Menyenangkan) method, integrated with a constructivist approach, on fifth-grade students' critical thinking skills and self-confidence in multiplication, and tested whether these effects differed across school levels. A quasi-experimental, one-group time-series design was used with 94 students purposively sampled from five public elementary schools in Kubutambahan District, Bali, representing high, medium, and low school levels. Students completed three repeated pretests, received treatment through GASING's concrete, abstract, and mental-arithmetic stages embedded in a constructivist sequence, and completed three repeated posttests using expert-validated instruments. Paired-samples t-tests showed statistically significant, very-large improvements in both critical thinking, t(93) = 26.40, p < .001, d = 2.72, N-Gain = 0.57, and self-confidence, t(93) = 39.99, p < .001, d = 4.12, N-Gain = 0.69. One-way ANOVAs revealed significant differences in gain across school levels for both outcomes: for critical thinking, medium-level schools gained significantly more than high-level schools, F(2, 91) = 4.27, p = .017; for self-confidence, both high- and medium-level schools gained significantly more than the low-level school, F(2, 91) = 16.01, p < .001. Non-parametric robustness checks corroborated all findings. These results confirm the effectiveness of the GASING-constructivist method for developing both competencies, while showing that the magnitude of benefit is moderated differently by school-level context, a nuance rarely examined in prior GASING research.]]>
