INTRODUCTION:Autism is associated with high cost to individuals, families, communities and government. Understanding educational and participation trajectories during the school years, and factors influencing these, is fundamental to reducing financial and personal costs. The primary aim of this study is to document the trajectories of Australian students with autism during their education. The secondary aim is to examine personal (eg, student skills) and environmental (eg, school setting) factors associated with differing trajectories and outcomes. METHODS AND ANALYSIS:The cross-sequential longitudinal study will recruit two cohorts of 120 parents/caregivers of children with autism. Cohort 1 aged between 4 and 5 years and cohort 2 between 9 and 10 years to start the study. Information will be gathered from parents, teachers and school principals at six annual time points (T1 to T6). Parents will be emailed a link to an online initial questionnaire (T1) and then contacted annually and asked to complete either an extended questionnaire (T3, T5 and T6) or an abbreviated questionnaire (T2, T4). Where consent is given, the child's current school will be contacted annually (T1 to T6) and teacher and school principal asked to complete questionnaires about the child and school. Parent and school questionnaires are comprised of questions about demographic and school factors that could influence trajectories and a battery of developmental and behavioural assessment tools designed to assess educational and participation trajectories and outcomes. Surveys will provide longitudinal data on educational and participation trajectories for children and adolescents with autism. In addition cross-sectional comparisons (within or between age groups) at each time point and cohort effects will be explored. ETHICS AND DISSEMINATION:Ethics approvals have been granted for this study by all recruiting sites and universities in the project. Study findings will inform policy and practice to promote successful inclusion and participation of children with autism in education. Results will be disseminated through journal publication, conference and seminar presentation.