<![CDATA[This study is motivated by the low critical thinking skills and cooperative attitudes among class XI TKR students at SMK Bunda Satria Wangon in the subject of Pemeliharaan Sasis dan Pemindah Tenaga Kendaraan Ringan (PSPTKR), particularly on the power transmission system material, due to the use of teacher-centered conventional learning models. This study aims to determine the difference in students' critical thinking skills before and after implementing the Project Based Learning (PjBL) model, and to determine whether student cooperative attitudes meet the good criteria through this model. The research method used is quantitative with a Nonequivalent Control Group Design. The research population comprised all class XI TKR students at SMK Bunda Satria Wangon, with a sample of 38 students in the experimental class and 36 students in the control class (74 students total). Data collection of critical thinking skills used a test instrument of 10 essay questions, while cooperative attitude data were collected through a questionnaire. Data analysis included descriptive analysis, prerequisite tests (normality and homogeneity), and inferential analysis using Paired Samples t-Test and Independent Samples t-Test. The results showed that there was a significant difference in students' critical thinking skills before and after using the PjBL model in the experimental class (t = 41.218, Sig. < 0.001). The experimental class showed a gain absolute of 21.21 points compared to 14.39 points in the control class. N-Gain scores for both classes were in the moderate category (experimental: 0.590; control: 0.587). Independent samples t-test results also showed a significant difference between the two classes (t = 6.335, Sig. = 0.000). These findings confirm that the PjBL learning model is effective in improving critical thinking skills and fostering cooperative attitudes among students on the power transmission system material.]]>
