This thesis explores the potential of Bronfenbrenner’s Bio-ecological Model of Human Development (Bronfenbrenner and Morris, 2006) as a framework for theory and research in psychology, sociology and education. It draws on other well-known conceptual approaches, particularly Bourdieu’s theories of social reproduction, habitus, field and cultural capital, investigating points of theoretical enhancement and synthesis. This culminates in the development of eight Propositions for a Bio-ecological Framework. These are then tested using data from a qualitative examination of two key educational transitions, pre-school to primary and primary to secondary school. Using qualitative methodologies, this research explores perspectives of children, teachers and parents in a case-study primary school in Ireland, the three pre-schools that feed into it, and the two secondary schools into which it feeds. The data are analysed using the Process-Person-Context-Time (PPCT) approach (Bronfenbrenner and Morris, 2006), and yield the key finding that relationships are crucial to positive transitions, perhaps even more important than the contexts in which they take place. Other findings emphasise the impact of diversity (cultural, socio-economic, etc), specific skills for traversing new settings, the importance of time, both personal and socio-historical, and the vital nature of supports for transition, locally and at policy-level. The research is particularly innovative in foregrounding the potential impacts of transition on parents, and their roles in supporting children at these times. Interestingly, the findings were remarkably similar for both transitions, regarding fears and hopes of parents and children. The Propositions of the Bio-ecological Framework are supported by the data, and so it may provide an appropriate conceptual basis for future work. The thesis concludes with recommendations for policy, research and practice.