In the context of an emerging new additional learning needs (ALN) system in Wales, this research explores who was likely to be identified with special educational needs (SEN) under the previous system. Our study reveals analysis of linked Welsh education and health data on SEN identification in learners in mainstream education settings born between 2002/3 and 2008/9. Using longitudinal multilevel modelling, we explore (i) who is likely identified with SEN and (ii) whether there is evidence of social patterning in SEN identification. We find that 48% of those born in the year 2002/3 were identified with SEN at some point during their schooling years. Furthermore, when controlling for health‐related variables, those who are identified with SEN in Wales were more likely to be male, White, from a deprived background, with lower school attendance, had not experienced breastfeeding and were born later in the academic year. Taken together, the research findings suggest that SEN identification was influenced by a child's context. The study thus underscores the critical importance of examining the relationship between socioeconomic, environmental and biological factors in SEN identification, urging for a comprehensive and cross‐organisation approach to enhance outcomes for learners with diverse needs. It also highlights the need for follow‐up research to explore unfolding trends as the new ALN system in Wales becomes fully implemented and integrated over the coming years.