Effectiveness of integrated STEM and problem-based learning in improving students’ conceptual understanding in science

Persistent gaps in Philippine science performance and competency demands under the Department of Education (DepEd) K-12 curriculum have signaled the need for interdisciplinary, problem-centered instruction. This study designed and evaluated an Integrated Science, Technology, Engineering, and Mathematics with Problem-Based Learning (I-STEM-PBL) module for General Biology 1 (Biomolecules) in Grade 11 Senior High School (SHS). The module was informed by the 3C3R problem design model (content, context, and connection; researching, reasoning, and reflecting; affect, difficulty, and teamwork) and adapted PBL scaffolds appropriate for SHS. Using a quasi-experimental one-group pretest–posttest design, Grade 11 STEM students (n = 38) completed the six-week intervention. Conceptual understanding served as the primary outcome. A paired-samples analysis showed statistically significant gains from pretest to posttest, with a medium effect size (Cohen's d = 0.539). These results indicate that the I-STEM-PBL module improved learners' understanding of biomolecules while remaining aligned with DepEd K–12 expectations. The findings contribute evidence that structured PBL, when integrated with explicit STEM connections and scaffolded inquiry, can enhance concept learning in senior high school biology.