School mental health programmes (SMHPs) have emerged as a critical area of focus in addressing the psychological and emotional needs of students in Nigerian schools. The study employs a mixed methods design with pre- and post-intervention assessments using validated psychometric scales for academic performance. Qualitative data are gathered through semi-structured interviews and focus group discussions, analysed thematically to identify common themes related to programme efficacy and perceived benefits. Findings indicate that students who participated in SMHPs showed a significant improvement (p < 0.05) in their overall academic performance compared to those not involved, with an average grade point increase of 0.7 points across all subjects. The mixed methods approach revealed a complementary relationship between the quantitative and qualitative data, providing robust evidence for the effectiveness of SMHPs in enhancing students' academic success. Based on these findings, it is recommended that school administrators integrate comprehensive mental health services into their curricula to support student well-being and academic achievement.