<![CDATA[Mathematical critical thinking is an essential competency that enables elementary students to analyze information, evaluate alternative solutions, and make reasoned decisions when solving mathematical problems. This study examined differences in mathematical critical-thinking performance between elementary students who learned through Project-Based Learning (PjBL) and those who received conventional instruction. A quasi-experimental study employing a posttest-only control group design involved 40 sixth-grade students, comprising 20 students in the experimental group and 20 in the control group. The experimental group received PjBL-based mathematics instruction, whereas the control group received conventional instruction. Data were collected using an essay-based mathematical critical-thinking test and analyzed using Welch’s independent-samples t-test to account for unequal variances between the groups. The results indicated a statistically significant difference in posttest scores, t(27.36) = 18.42, p < .001, with a mean difference of 25.40 points (95% CI [22.57, 28.23]). The experimental group achieved a higher mean score (M = 90.0) than the control group (M = 64.6), with a very large effect size (Hedges’ g = 5.71). These findings indicate that students who participated in PjBL demonstrated substantially higher observed mathematical critical-thinking performance than those who received conventional instruction. This study provides context-specific empirical evidence supporting the use of carefully designed PjBL in elementary mathematics, particularly when project activities are aligned with mathematical learning objectives and supported by appropriate teacher guidance.]]>
