Effectiveness of a Universal, Classroom-Based Preventive Intervention (PAX GBG) in Estonia: a Cluster-Randomized...

The PAX Good Behavior Game (PAX GBG) is a behavior management strategy that has demonstrated positive effects on children's behavior and well-being in trials conducted mainly in the USA. This study assessed the impact of the PAX GBG on students' mental health and behavior 7 and 19 months post-baseline in Estonia. This matched-pair, cluster-randomized, waitlist-controlled, open-label trial included 42 Estonian elementary schools with 708 first-grade students. The primary outcome was children's overall mental health rated by teachers, while secondary objectives were to examine whether the effects of the intervention extended to the home context. Teachers also rated their self-efficacy and overall classroom behavior. Intervention adherence and children's exposure to the intervention were also measured. Modified intention to treat analysis involved 696 students on first post-baseline and 647 on second post-baseline. Intervention had positive effects on children's mental health at the end of the first academic year, which lasted and strengthened during the second academic year. Moderation analysis demonstrated positive effects on mental health and prosocial behavior for high-risk students during the first year. A few positive effects extended to the home environment during the second academic year. Implementation fidelity was satisfactory. The intervention also had a positive lasting effect on teacher's self-efficacy and overall classroom behavior. This study shows the positive effects of the PAX GBG in Estonian schools and supports broader implementation of the intervention in Estonian elementary schools. TRIAL REGISTRATION: ClinicalTrials.gov No. NCT02865603.