There is a growing consensus amongst policy makers, education professionals, researchers, and the public that a modern education system should develop a 'whole child' providing a balanced set of cognitive, social and emotional skills to face the challenges of an increasingly uncertain and volatile world. Social and emotional development are educational goals in and of themselves, as well as important influences on academic learning. There is currently a gap in knowledge about social and emotional development and academic performance, particularly in the middle years. The primary to secondary school transition is a time when children, particularly those with vulnerabilities, need strong social and educational support systems. Despite this, there are currently few evidence-based, system-wide strategies to support students in the transition. This report examines changes in student wellbeing and learning across the middle years, drawing on recent longitudinal data on Australian students from the Childhood to Adolescence Transition Study (CATS). The CATS sample comprises over 1200 students and their parents recruited in 2012 from schools in metropolitan Melbourne. The study has obtained information annually from students, parents and teachers around students' mental health and wellbeing, peer and family relationships, school engagement, and the primary to secondary school transition. This report analyses data collected between Year 3 (2012: 8-9 years of age) and Year 7 (2016; 12-13 years of age). Guided by a conceptual model of quality education, this report uses a number of indicators of student learning, wellbeing and school engagement to examine how these intersect in the middle years. The longitudinal dataset is used to address the following questions: (1) To what degree does student wellbeing in the middle years influence school engagement and learning? (2) To what degree does student learning in the middle years influence school engagement? (3) To what degree do peer relationships in the middle years influence school engagement and learning? The report also describes the experience of students and parents during the secondary school transition. It reports on readiness for secondary school prior to transition in Year 6 and observed adjustment to secondary school in Year 7, and investigates teachers' ability to identify students at risk of a poor transition. The report also examines the support received by students and parents from schools and how this relates to adjustment in secondary school. This report is guided by a framework of quality education in which student wellbeing, school engagement and learning are all important and inter-related. The results from this report confirm the reciprocal relationships between wellbeing, engagement and learning. These findings suggest that by working on all three aspects simultaneously, schools and education systems will achieve synergies in their efforts to provide quality education. In demonstrating the relationship between wellbeing and school engagement and learning outcomes, this report provides strong motivation for education systems, schools and teachers to promote the social and emotional development of students to help each and every student reach their full learning potential. A glossary is provided. [The CATS study received funding from the National Health and Medical Research Council, Australian Rotary Health, the Invergowrie Foundation, and the Department of Education and Training (Victoria). The Murdoch Children's Research Institute's (MCRI) research is supported by the Victorian Government's Operational Infrastructure Program. The Centre for Adolescent Health is a research group of the Murdoch Children's Research Institute.]