A longitudinal study was conducted over four stages of three school years across the primary-secondary transition. The purpose was to understand the dynamic transition experience of pupils, investigate the effectiveness of preparation by schools to support transitions and understand pupils' most important support networks. Using online questionnaires, data were collected from pupils at four time points, twice from secondary school professionals and their parents, and once from primary school professionals. Results highlight the ongoing and dynamic nature of transitions. What pupils were excited about were still seen to be good once they were in secondary school, and aspects that worried them declined over time. Some pupils experienced problems and adapted at different times, whereas for some, problems emerged later. It seems that those who anticipated problems when in primary school were more likely to experience problems; this has implications for the discourse around transitions and its impact on pupils' anticipation of transition experience. Although transition planning and preparation by schools were important and varied, they were not always effective, not provided in a timely manner and did not tap into their naturally occurring support networks in the home and community. This study makes unique contributions in terms of highlighting the dynamic transitions process and change in pupils' experience over time; various aspects of transitions that children are excited and concerned about and how these changed over time; professionals' conceptualisations of transitions; pupils' and parents' views of the effectiveness of transition practices at various stages; and pupils' real support networks.