<![CDATA[In the 21st century, mathematical critical thinking is a core competency that students must master. However, high school students still struggle to analyze word problems in mathematics. This study examines how students’ mathematical critical thinking skills develop over three Project-Based Learning (PjBL) sessions on probability. The study employs a quantitative approach with a pre-experimental, single-group repeated measures (time-series) design, involving 35 10th-grade students at SMAN 3 Kediri (Public Senior High School 3 Kediri). Data were collected through essay-based word-problem tests at the end of each session and assessed using a rubric based on the six FRISCO indicators (Focus, Reasoning, Inference, Situation, Clarity, and Overview), adapted from Ennis. The data were analyzed using the nonparametric Friedman and Wilcoxon Signed-Rank tests because the distributions of Test 2 and Test 3 scores deviated from normality. Average scores increased gradually from 59.86 (Test 1) to 61.61 (Test 2) and 69.04 (Test 3), with a statistically significant increase only observed from Test 2 to Test 3. At the indicator level, “Focus” and “Situation” increased sharply in the third session; “Reason” remained the strongest indicator, while “Inference” and “Overview” remained the weakest. These findings suggest that students’ mathematical critical thinking skills developed gradually throughout the PjBL sequence, although the single-group design without a control group limits causal claims regarding PjBL’s contribution. Teachers are advised to supplement PjBL with explicit scaffolding during the inference and answer evaluation stages.]]>
