The issue of poor academic performance among secondary school students in Nigeria, particularly in densely populated classrooms, has raised concerns among educators and stakeholders. This study aims to investigate the relationship between class size, school population, and student academic achievement in the Agege Local Government Area of Lagos State. Drawing on previous literature and research findings, the study addresses the challenges associated with overpopulation in classrooms, including limited individual attention, compromised teaching effectiveness, and inadequate resources. Using a descriptive research design, data will be collected from a sample of secondary school teachers and students through a structured questionnaire. The analysis will involve examining the correlation between class size, school population, and academic performance, as well as the impact of overpopulation on classroom management and school resources. The findings of this study are expected to contribute to the understanding of factors influencing student achievement in overcrowded classrooms, providing insights for educators, policymakers, and educational planners to address these challenges effectively.