School nutrition programmes in Kenya have been implemented to improve adolescent health outcomes, including HIV/AIDS prevention education. These programmes aim to enhance knowledge and participation rates among students. A mixed-methods approach was employed, combining quantitative data from surveys with qualitative insights from focus group discussions. Data were collected from a sample of Kenyan schools to assess programme impact. Adolescent participation in nutrition programmes varied significantly across schools, with participation rates ranging between 45% and 70%. Knowledge gains related to HIV/AIDS prevention were observed among participants. The study highlights the importance of tailored interventions that consider adolescent engagement for effective HIV/AIDS prevention education. School nutrition programmes should incorporate strategies to increase participant engagement, particularly targeting adolescents who are less likely to participate. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.