In Northern Ghana, adolescent mental health issues are prevalent but often underdiagnosed, leading to poor academic performance and social isolation. A longitudinal study was conducted with 500 participants randomly selected from 10 schools. Data were collected through pre- and post-intervention surveys measuring mental health symptoms, academic achievement, and socioeconomic status. There was a statistically significant increase (p < 0.05) in students' overall GPA scores by 20% after the intervention compared to baseline. School-based mental health interventions can improve academic performance among adolescents in Northern Ghana, with a notable improvement in grades. Further studies should explore long-term effects and cost-effectiveness of such interventions. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.