Science teaching in general and physics teaching in particular often fail to meet the challenges of motivating and engaging learners. Consequently, students do not adequately understand concepts, leading to the poor acquisition of expected practical skills. In response to this need, we conducted a study to document physics teachers' instructional practices and students' learning environments in Rwandan secondary schools. We used the Classroom Observation Protocol for Undergraduate STEM to collect data. For three months, we observed 34 geometric optics lessons for nine Senior-4 Physics teachers and 28 physical optics lessons for seven senior-5 Physics teachers. The results indicate that learner-learner active engagement during group work takes 19% of a 2 min time interval. In comparison, learner-teacher active engagement during teacher guide and questioning take 36.8% and 46.5% of a 2 min time interval, respectively. How teachers and students spend time on each classroom activity was analysed, and recommendations for student engagement were also discussed.