Background The evidence is now quite clear that bullying in schools is an international problem. Bullying is widely regarded as a particularly destructive form of aggression, with harmful physical, social and emotional outcomes for all involved (bullies, victims and bystanders), and with particular risks for children with special needs. The research of the past 25 years confirms its widespread nature where it is most likely in groups from which the potential victim cannot escape—e.g. schools. In 1994 an Australian Commonwealth Government inquiry, following on from the pioneering work of research documented by Smith and co-workers, heralded a growing awareness of the need to address the issue of school violence, particularly bullying. Internationally, researchers have identified the impact of intervention programmes to reduce school bullying. In Australia a nationally and internationally used, systemically based intervention programme called the PEACE Pack, has previously been shown to be effective in reducing bullying in primary schools. Purpose The purpose of the present study was to provide further supporting longitudinal evidence regarding the efficacy of the PEACE Pack in markedly reducing bullying among young children of junior primary and primary school age. Further, the study also identified the characteristics of a small group of children who do not appear to benefit from intervention efforts. Finally, in this paper, a computer-based innovation for collecting school-based data regarding student perceptions of bullying is described. Sample The sample of 954 pupils comprised 458 males and 496 females from four Australian primary schools in Adelaide, a large metropolitan city in Australia. The pupils ranged in age from 5.4 to 13.5 years. Design and methods The study involved a pre- and post-test design and the administration of a questionnaire to evaluate the effectiveness of the implementation of the PEACE Pack programme to address the issue of school bullying. Results The interventions were effective in reducing the level of school bullying in the junior primary and primary schools, although there were variations in the gains achieved across the age range and across the four schools. Conclusions In the present study the systemic PEACE Pack interventions resulted in approximately one-fifth of pupils in the overall sample reporting that they were being bullied ‘less’ as a result of year-long interventions. This effect was greatest in the primary schools, particularly for boys. Consideration was given to a small group of students who reported being bullied ‘more’ after the interventions, and to the development of a computer-based assessment procedure for assessing the extent of bullying in schools.