The impact of school-based sex education programmes on adolescent reproductive health knowledge in Kigali schools was evaluated over a three-year period. A quantitative survey methodology was employed, including structured questionnaires administered to students aged 13-18 years from randomly selected schools. Data were collected at three time points over a period spanning the entire academic year. Students showed significant improvements in knowledge about reproductive health topics post-intervention, with an average increase of 25% in correct responses across all tested areas. School-based sex education programmes have a positive impact on adolescent reproductive health knowledge but require ongoing evaluation and refinement to maintain effectiveness. Regular updates to curriculum content are recommended based on current research and best practices, along with periodic assessments of student understanding and engagement levels.