Abstract
Critical thinking skills are essential skills that students must have in solving the diverse challenges they will face. The reality found is that students have low critical thinking skills. Students need to be trained to analyze and solve problems. One alternative is using the inquiry learning model. This research is Classroom Action Research, which aims to see the increase of students' critical thinking skills. The research subject was class X E.5 at SMAN 7 Padang. It was carried out over 2 cycles, with the design of the research being the Kemmis and McTaggart model. The data collection techniques used were observation, interviews, and written tests. The research instruments used were critical thinking skills observation sheets and written test questions. The average value of students' critical thinking skills in the pre-cycle was 50.6% with low criteria, the results in cycle 1 with a percentage value of 66.98% in the medium category, and cycle 2 increased to 73.30% in the skills category high critical thinking. From these results, it can be inferred that the inquiry learning model can be used in the learning process to increase student's critical thinking skills.