Background
The ‘long shadow’ of childhood bullying can extend beyond immediate adverse mental health and educational outcomes well into adulthood, with associated long-term health and social care costs. Reducing bullying is therefore a public health priority.

KiVa, a school-based anti-bullying programme, is effective in reducing bullying in schools in Finland and is currently being tested in the UK through the large-scale Stand Together trial.

Methods
The Stand Together trial is a two-arm, pragmatic multicentre cluster randomised controlled trial (RCT) to test the effectiveness and cost-effectiveness of KiVa in reducing bullying in UK primary schools compared to usual practice over one academic year. The trial is targeting approximately 13,000 7- to 11-year-olds in 116 primary schools across England and Wales, including North Wales, the West Midlands, South East- and South West England. Usual practice is defined as the delivery of the Personal and Social Education (PSE) curriculum in Wales and the Personal, Social, Health and Economic (PSHE) Education in England.

To assess cost-effectiveness, we are conducting a cost-utility analysis and wider cost-consequence analysis from a school and societal perspective. Pupil self-reported health-related quality of life (CHU9D) is the primary outcome to enable the calculation of quality-adjusted life years (QALYs) in an Incremental Cost Effectiveness Ratio (ICER). The cost-consequence analysis will consider other outcomes such as pupil self-reported bullying-victimisation, pupil absence and bullying-related service use, teacher wellbeing and the frequency of parent-school meetings regarding bullying.