Undernourished primary school children in West African countries often experience weight gain following nutrition interventions. A comprehensive search of peer-reviewed databases was performed, including PubMed and Scopus. Studies were screened based on eligibility criteria to identify relevant articles for synthesis. The review identified several studies reporting significant weight gain among undernourished Ethiopian primary school children over a three-year period, with an average increase in body mass index (BMI) of 10%. School-based nutrition interventions appear effective in promoting weight gain in undernourished Ethiopian primary school children. Further longitudinal studies are recommended to validate these findings and explore the long-term effects 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.