Abstract Introduction Psychotic experiences (PEs) are associated with increased risk of later mental disorders and so could be valuable in prevention studies. However, to date few intervention studies have examined PEs. Given this lack of evidence, in the current study a secondary data analysis was conducted on a clustered-randomized control trial (RCT) of 3 school based interventions to reduce suicidal behaviour, to investigate if these may reduce rates of PEs, and prevent PE, at 3-month and 1-year follow-up. Methods The Irish site of the Saving and Empowering Young Lives in Europe study, trial registration (DRKS00000214), a cluster-RCT designed to examine the effect of school-based interventions on suicidal thoughts and behaviour. Seventeen schools (n = 1096) were randomly assigned to one of three intervention arms or a control arm. The interventions included a teacher training (gate-keeper) intervention, an interactive educational (universal-education) intervention, and a screening and integrated referral (selective-indicative) intervention. The primary outcome of this secondary data-analysis was reduction in point-prevalence of PEs at 12 months. A second analysis excluding those with PEs at baseline was conducted to examine prevention of PEs. Additional analysis was conducted of change in depression and anxiety scores (comparing those with/without PEs) in each arm of the intervention. Statistical analyses were conducted using mixed-effects modelling. Results At 12-months, the screening and referral intervention was associated with a significant reduction in PEs (OR:0.12,95%CI[0.02–0.62]) compared to the control arm. The teacher training and education intervention did not show this effect. Prevention was also observed only in the screening and referral arm (OR:0.30,95%CI[0.09–0.97]). Participants with PEs showed higher levels of depression and anxiety symptoms, compared to those without, and different responses to the screening and referral intervention & universal-education intervention. Conclusions This study provides the first evidence for a school based intervention that reduce & prevent PEs in adolescence. This intervention is a combination of a school-based screening for psychopathology and subsequent referral intervention significantly reduced PEs in adolescents. Although further research is needed, our findings point to the effectiveness of school-based programmes for prevention of future mental health problems.