Adolescents in South African townships often lack comprehensive reproductive health knowledge, leading to increased vulnerability to sexually transmitted infections (STIs) and unintended pregnancies. A quasi-experimental design was employed with pre- and post-test assessments, stratified by gender to ensure balanced representation. A total of 500 students from four randomly chosen schools were enrolled. Post-intervention surveys revealed a statistically significant improvement in knowledge scores, particularly among girls (p < 0.01; 95% CI: [0.46, 0.78]), indicating the effectiveness of sex education programmes in addressing reproductive health gaps. School-based sex education programmes have demonstrated positive outcomes in increasing adolescent reproductive health knowledge, warranting continued implementation and possibly gender-specific tailoring to address disparities effectively. Implementers should consider incorporating interactive elements into curricula and regularly updating content based on current research and community needs. Policy makers are encouraged to fund and mandate comprehensive sex education in schools. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.