<![CDATA[Critical thinking skills involve logical and reasonable thinking activities that focus on making informed decisions regarding problems faced. Based on the results of observations carried out in class XI-8 SMA Negeri 2 Kediri, the data obtained indicate that the level of critical thinking skills among students is 50.7%. To overcome the problem, an effective learning model is needed to improve students' critical thinking skills, namely the ASICC learning model (Adapting, Searching, Interpreting, Creating & Communicating) which guides students to be able to reflect on themselves to achieve learning objectives, collect key information, solve contextual problems, share ideas, and produce a certain product. The purpose of this study is to determine the improvement of critical thinking skills of class XI-8 students of SMAN 2 Kediri on biology material through the ASICC learning model based on Lesson Study. This study employed a classroom action research (CAR) method, combined with lesson study, as described by Kemmis and McTaggart, and was conducted at SMAN 2 Kediri from February 2025 to March 2025. The data processed shows an increase in students' critical thinking. Data were collected through observations, interviews, post-test questions, and an assessment rubric. This research was analyzed using Zubaidah's Essential Skills of Thinking rubric. This study revealed an increase in students' critical thinking skills, from 62.4% in cycle 1 to 76.8% in cycle 2. Keywords: ASICC, Critical thinking skills]]>
