This study presents a comparative analysis of English teachers' experiences under the Revised Basic Education Curriculum (RBEC) and the K-12 curriculum in the Philippines. By employing a convergent mixed-method approach, the research investigates the participants’ perspectives on student behavior and teachers' experiences in curriculum adaptations. Quantitative data were gathered from twenty English teachers using a Likert-scale survey, while qualitative insights were obtained through in-depth interviews with ten teachers. Results indicate that the K-12 curriculum enhances student engagement, interaction, and academic performance compared to RBEC, but also introduces challenges related to curriculum complexity and resource demands. Teachers reported significant changes in instructional practices, driven by the need to meet new content standards and integrate technology effectively. The study highlights the necessity for continuous professional development and resource support to address these challenges. The findings offer valuable insights for policymakers and educators in refining curriculum strategies to improve educational outcomes. The transition from RBEC to K-12 marks a crucial step in aligning the Philippine educational system with global standards. However, it underscores the need for on-going evaluation and support for teachers to maximize the curriculum's potential benefits.

Keywords: Revised Basic Education Curriculum (RBEC), K-12 Curriculum, English Teachers, Curriculum Transition, Philippine Education System, Student Behavior, Comparative Analysis, Teacher Experiences, Educational Reform