<![CDATA[The study examined the effect of implementing the Treffinger learning model with an open-ended approach on students’ critical thinking skills in ecology and Indonesian biodiversity topics. It used a quantitative method with a quasi-experimental nonequivalent control group design. The participants were seventh-grade students of Junior High School 24 Surakarta in the 2024/2025 academic year. Two classes were selected through cluster random sampling, with 30 students of Grade 7C played as the experimental group, taught using the Treffinger model with an open-ended approach. Meanwhile, 30 students of Grade 7D played as the control group, taught using the discovery learning model. Data were collected using pre-test and post-test instruments. Before the study, all samples were through an initial equivalence test to ensure the groups had similar baseline conditions. The validity of the instruments was confirmed using the Gregory test and the Product Moment correlation, while reliability was assessed using Cronbach’s alpha. It indicated a high to very high reliability. The pre-test and post-test scores were subsequently tested for normality and homogeneity. Data analysis using an independent samples t-test revealed a significant difference in students’ critical thinking skills between the experimental and control groups (p < 0.05). In addition, the means of pre-test and post-test scores of the experimental group were higher than those of the control group. The findings demonstrated that the Treffinger learning model, integrated with an open-ended approach, significantly enhanced students’ critical thinking skills in science learning]]>
