Inequities in learning, development and health are evident when children start school. These trajectories track into adulthood with consequent poorer educational, health and social outcomes. Māori and Pacific and children from disadvantaged communities are disproportionately affected. These outcomes are unjust and costly for society. The universal free Well Child Tāmariki Ora Programme (WCTO) is designed to identify developmental concerns so early intervention can maximise outcomes. Emerging evidence suggests the mandated developmental surveillance tool, the Parental Evaluation of Developmental Status (PEDS), is not performing as it should, potentially increasing inequities. Of concern, the PEDS has not been standardised nor validated in NZ. This research explores parental understanding of child development and how it is assessed, and examines the validity of the PEDS for NZ populations and therefore its appropriateness. Findings will have a direct impact on the redesign and future delivery of the WCTO programme to ensure it reduces inequities and achieves better outcomes for all tāmariki.