In Australia and many other countries, the provision of the healthiest possible start in life for all children has been a priority for government. Evidence to support the importance of the early years for future development has accumulated over the past two decades [1]. Patterns of childhood development predict health, wellbeing, learning and behaviour and lay a foundation for children to grow up with the skills to succeed, bringing benefits for them and the community as a whole [2]. The Australian Early Development Census (AEDC) is one major investment within the national agenda for early childhood development. It provides information to communities, governments and schools to support their planning and service provision. It also allows identification of groups of students who are developmentally vulnerable (DV) when entering the education system. This report presents findings from a linkage study involving the 2009 AEDC and CATS (Childhood to Adolescence Transition Study) datasets. CATS is an ongoing longitudinal study of health, wellbeing and educational achievement through late childhood and early adolescence. The sample comprises over 1,200 students and their parents drawn from Year 3 in 2012 from randomly selected schools across metropolitan Melbourne. The authors obtained information annually from students, parents and teachers on students' mental health and wellbeing, peer and family relationships, school engagement and the primary to secondary school transition. Guided by the conceptual framework described in our previous report, the current report uses a linked longitudinal dataset of student development and academic achievement spanning the entire primary school years (from the first year of primary school; 5-6 years of age through to Year 7; 12-13 years of age) to address the following questions: (1) What is the relationship between early developmental vulnerability on the AEDC and later learning, school engagement and wellbeing? (2) How might any relationship between early developmental vulnerability and learning at Year 7 be affected by wellbeing and school engagement across Years 3, 4 and 5? [This report was undertaken by the Centre for Adolescent Health on behalf of the Evidence and Assessment Group, the Australian Government Department of Education and Training. The Centre for Adolescent Health is a research group of the Murdoch Children's Research Institute.]