In this study, we used a research tool for measuring students' conceptual understanding in optics, the Geometrical Optics Conceptual Understanding Test-2 (GOCUT-2), to evaluate the impact of supplementing classroom instruction with laboratory experiments, PhET simulations, or YouTube videos. This study involved students from public, urban secondary schools in Rwanda. Preliminary findings from the study indicate that these instructional resources did impact student conceptual understanding, and this impact is not uniform across all topics covered in geometric optics. A MANOVA demonstrated that learning outcomes were best for students who combined traditional physics labs with digital tools. This analysis also indicates that schools, where physics laboratories were most used, were more likely to exhibit greater conceptual understanding. We observed similar increases when PhET simulations and YouTube video resources were used together. In each case, students still showed some gaps related to drawing and interpreting images formed by lenses. We recommend that teachers supplement the geometric optics curriculum with open educational resources (OERs), including PhET simulations and YouTube videos.