Adolescents in Ghanaian secondary schools face challenges related to sexual reproductive health (SRH), including limited knowledge and access to contraceptive methods. The study employed a pre- and post-intervention design with quantitative surveys conducted among adolescents. Data were analysed using descriptive statistics and chi-square tests for significance testing. Among the surveyed students, there was an increase of 25% in contraceptive knowledge scores after the intervention (mean score: 78 out of 100 pre-intervention, 93 post-intervention). The school-based intervention significantly improved adolescent SRH knowledge and access to contraceptives. Policy makers should prioritise comprehensive sexual education programmes in schools and ensure equitable access to reproductive health services for adolescents. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.