Early childhood education in Nairobi's slums is a critical area of focus due to its significant impact on long-term socio-economic development. The study employed mixed-methods, including quantitative surveys and qualitative interviews with parents, teachers, and children to assess programme impact. A key finding was that structured play-based learning programmes significantly improved cognitive skills among participating children by an average of 20% compared to non-participants in the same age bracket. The findings suggest that well-designed educational interventions can lead to substantial improvements in early childhood development outcomes, particularly in socio-economically disadvantaged areas. NGOs should continue and expand their programmes, especially focusing on community engagement and sustainability strategies.