This longitudinal prospective cohort study was conducted to determine the impact of effective science instruction on performance on high-stakes high school graduation assessments in science. This study provides powerful findings to support authentic science teaching to enhance long-term retention of learning and performance on state-mandated assessments. Students experienced some combination of zero to three effective teachers throughout their middle school experience. Findings revealed that all students who experienced effective science teachers who engaged students in inquiry-based science outperformed students who had less effective teachers. Additionally, those who had more effective teachers over time performed increasingly better. Implications for stakeholders will be discussed. (Contains 4 tables.)