Background: If the window of opportunity presented by the early years is missed, it becomes increasingly difficult to create a successful life-course. A biopsychosocial model of special educational need with an emphasis on participation and functioning moves the frame of reference from the clinic to the school and the focus from specific conditions to creating supportive environments cognisant of the needs of all children. However, evidence suggests that an emphasis on diagnosed conditions persists and that the needs of children who do not meet these criteria are not identified. The Early Development Instrument (EDI) is a well-validated, teacher-completed population-level measure of five domains of child development. It is uniquely placed, at the interface between health and education, to explore the developmental status of children with additional challenges within a typically developing population. The aim of this study was to examine the extent to which the special educational needs of children in their first year of formal education have been identified. Methods: This cross-sectional study was conducted in Ireland in 2011. EDI (teacher completed) scores were calculated for 1344 children. Data were also collected on special needs and on children identified by the teacher as needing assessment. Mean developmental scores were compared using one-way ANOVA. Results: Eighty-three children in the sample population (6.2%) had identified special educational needs. A further 132 children were judged by the teacher as needing assessment. Children with special needs had lower mean scores than typically developing children, in all five developmental domains. Children considered by the teacher as needing assessment also had lower scores, which were not significantly different from those of children with special needs. Speech, emotional or behavioural difficulties were the most commonly reported problems among children needing further assessment. There was also a social gradient among this group. Conclusions: A small but significant number of children have not had their needs adequately assessed. Teacher observation is an effective means of identifying children with a level of impairment which prevents them from fully participating in their educational environment and could be integrated into a multi-disciplinary approach to meeting the needs of all children.