BackgroundInvolvement of parents/carers may increase the effectiveness of primary school-based alcohol-misuse prevention projects. However, few interventions have been designed for pre-adolescent children, or specifically involve parents/carers. The Kids, Adults Together (KAT) programme in primary schools aimed to reduce alcohol misuse through such an approach.ObjectiveTo determine the value and feasibility of conducting an effectiveness trial of KAT.DesignParallel-group cluster randomised exploratory trial with an embedded process evaluation. Schools were the unit of randomisation.SettingPrimary schools (n = 9) in south Wales, UK.ParticipantsPupils in Year 5/6 (aged 9–11 years) and their parents/carers; school staff.InterventionThe Kids, Adults Together programme consisted of (1) classwork addressing the effects of alcohol; (2) a family event for children and parents/carers; and (3) a ‘goody bag’ containing fun items, including a digital versatile disc (DVD) for families to watch together. The intervention comprised KAT plus existing alcohol-related activities and lessons. Control-group schools continued with existing alcohol-related lessons and activities.Main outcome measuresKey outcomes related to the progression criteria for a potential future effectiveness trial. These included the acceptability, participation equity, feasibility and implementation of KAT; the recruitment and retention of research participants; and the acceptability and feasibility of research processes, including data collection methods and outcome measures.ResultsNine schools (free school meal entitlement ranging from 1% to 37.2%) participated. Two of five intervention schools withdrew but all four control schools were retained, and these seven schools facilitated all research data collections. Programme acceptability and participation rates were high in all three intervention schools (parent/carer participation rates ranged from 45.1% to 65.7%), although implementation quality varied. At baseline, approximately 75% of eligible children (n = 418) provided data, of whom 257 also provided data at follow-up. Only 27 parents/carers (estimated response rate 6.5%) completed interviews. Most children were willing to complete questionnaires but measures were not appropriate for this age group. Measures of alcohol consumption produced inconsistent responses. Intermediate outcomes on family communication showed no evidence of intervention effectiveness.ConclusionsIn the three schools that received the KAT intervention, it was found to be acceptable to schools and pupils and there were good levels of participation from parents/carers from across a range of socioeconomic groups. However, two intervention schools withdrew from the trial. Findings from intermediate outcomes on family communication did not support programme theory. In addition, the study highlighted challenges in identifying suitable outcome measures for children aged 9–11 years and the feasibility of long-term follow-up via secondary schools.Future workIt would not be appropriate to proceed to an effectiveness trial of KAT. There are doubts/uncertainties about the potential effects of KAT; suitability of measures; the large number of schools which would be required for an effectiveness trial of KAT, and the cost of this; feasibility of follow-up in secondary schools; and programme implementation and theory. There is a need to develop and validate measures for children aged 9–11 years; to test the feasibility of follow-up data collection methods in secondary schools; and to further consider sample size requirements and feasibility.Trial registrationCurrent Controlled Trials ISRCTN80672127.FundingThe exploratory trial of this project was funded by the National Institute for Health Research Public Health Research programme and the process evaluation was funded by the Economic and Social Research Council. The work was undertaken with the support of The Centre for the Development and Evaluation of Complex Interventions for Public Health Improvement (DECIPHer), a UK Clinical Research Collaboration Public Health Research Centre of Excellence. Joint funding (MR/KO232331/1) from the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, the Welsh Government and the Wellcome Trust, under the auspices of the UK Clinical Research Collaboration, is gratefully acknowledged. This project will be published in full inPublic Health Research; Vol. 3, No. 15. See the NIHR Journals Library website for further project information.