Early childhood development (ECD) programmes in schools are increasingly recognised as crucial for child welfare and educational outcomes. A mixed-methods approach was employed, including qualitative interviews with teachers and parents as well as quantitative assessments of children’s developmental milestones. Children in ECD programme schools exhibited a significant improvement (p<0.05) in vocabulary acquisition compared to those not enrolled, indicating the programmes' positive effect on early literacy skills. The study underscores the importance of integrating comprehensive ECD initiatives into school curricula for fostering children's cognitive and social-emotional growth. Policy makers should prioritise funding and support for these programmes to ensure equitable access and sustained development outcomes among Kenyan children.