Mobile learning applications are increasingly used to educate adolescents on health topics such as reproductive health. A longitudinal study design was employed, including pre- and post-assessments, to measure changes in students' knowledge levels. Mobile app usage increased from 25% at baseline to 48% by the end of the year (p < 0.01), indicating significant uptake. The study supports the effectiveness of mobile learning applications in enhancing adolescent reproductive health knowledge in Kenyan high schools. Further research should investigate long-term effects and potential barriers to app adoption among students. adolescent reproductive health, mobile learning apps, behaviour change, longitudinal study Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.