Abstract. This study investigated the effectiveness of flipped classroom instruction compared to lecture-based instruction in enhancing Grade 9 students’ understanding of physics concepts. The limited research on the comparative effectiveness of flipped classroom instruction and lecture-based instruction in K-12 Philippine science education, along with the challenge of teacher-created video production, highlights a gap in understanding their practical implementation and impact. The researcher employed a quasi-experimental design, using a one-stage cluster sampling technique to assign 61 students to experimental and control groups randomly. Both groups demonstrated comparable prior knowledge based on their Third Quarter Science 9 performance, verified through a Mean Performance Score (MPS) analysis and a t-test: Two-Sample Assuming Equal Variances. Data treatment involved using the Mean, t-test for dependent data, and t-test for independent data. The findings revealed that while both instructional methods significantly improved student performance, the flipped classroom approach yielded higher post-test results than lecture-based instruction. The study concluded that flipped classroom instruction is a more effective strategy for fostering active learning and improving comprehension of key physics topics, such as projectile motion, impulse and momentum, linear momentum conservation, and mechanical energy conservation. The research encourages future researchers to replicate this study in other educational settings and expand its scope by exploring additional factors that influence the effectiveness of flipped classroom instruction.

Keywords: Flipped classroom; Lecture-based instruction; Grade 9 Science; Physics; Curriculum development.