<![CDATA[The critical thinking skills of elementary school students in Indonesia remain relatively low, particularly in Social Studies (IPS) content. This study aimed to develop Problem Based Learning (PBL)-based Student Worksheets (LKPD) that are valid, practical, and effective for improving fifth-grade students' critical thinking skills on the topic "My Proud Region." The research employed a Research and Development (R&D) approach using the ADDIE model, involving 52 fifth-grade students from UPT SDN 1 Kebon Jeruk. Data collection techniques included observation, questionnaires, and critical thinking ability tests in the form of pretests and posttests. The results demonstrated that the LKPD was declared highly valid, with average scores of 0.85 from material experts, 0.84 from language experts, and 0.85 from media experts. The LKPD was also deemed highly practical based on teacher responses (90.91%) and student responses (88.64%). Effectiveness was evidenced by the Independent Samples t-test (Sig. 0.000 < 0.05), an N-Gain improvement of 0.64, and an effect size of 1.358 (strong effect), which indicates that the PBL-based LKPD was associated with significant improvements in students' critical thinking skills. The study concludes that the developed PBL-based LKPD meets the criteria of being valid, practical, and effective for improving students' critical thinking skills in fifth-grade elementary school social studies content. This research contributes to instructional design by demonstrating the systematic integration of PBL syntax with critical thinking indicators, offering a replicable model for developing higher-order thinking-oriented teaching materials in elementary education.]]>
