The International Development and Early Learning Assessment (IDELA) was utilized in the Vietnam Sponsorship Program (VSP) to assess and track the developmental progress of preschool children. Specifically, IDELA measured key skills in motor development, early literacy, early numeracy, and socio-emotional areas among children aged 3-6 in remote districts of Lao Cai province. The tool was integral to evaluating the impact of VSP's educational interventions, such as the Early Literacy and Math (ELM) program. Over time, IDELA results demonstrated significant improvements in children's learning outcomes, including school readiness and enhanced literacy and numeracy skills. These results informed program adjustments and contributed to the evidence-based scaling of interventions. IDELA's findings underscored its value as a robust tool for monitoring the effectiveness of child development initiatives in challenging contexts, guiding strategies for capacity building, community engagement, and improving learning environments both at school and at home.