Implementation matters: Using complier average causal effect estimation to determine the impact of the Promoting Alternative Thinking Strategies (PATHS) curriculum on children’s quality of life.

This cluster randomized trial evaluated the impact of the Promoting Alternative Thinking Strategies (PATHS) curriculum on children's psychological wellbeing, peer social support, and school connectedness.Forty-five schools in England were randomly assigned to implement PATHS or continue their usual provision for 2 years.The trial sample was 5,218 students, aged 7-9 at baseline (M ϭ 8.12, SD ϭ .87).Teachers in PATHS schools received initial training and ongoing implementation support and assistance from trained coaches.Multilevel intent-to-treat (ITT) analysis of outcome data indicated that PATHS led to a small, statistically significantly improvement in children's psychological wellbeing but had no discernible impact on their peer social support or school connectedness.Multilevel complier average causal effect estimation using dosage as a compliance marker increased the intervention effect size for psychological wellbeing and revealed significant medium to large effects for peer social support and school connectedness.The implications of these findings are discussed, and study limitations are noted. Educational Impact and Implications StatementThis study demonstrates that the Promoting Alternative Thinking Strategies (PATHS) curriculum significantly improves children's psychological wellbeing, but also social peer support and school connectedness, once intervention compliance is considered.Thus, social and emotional learning interventions such as PATHS can be considered an efficacious means for promoting these outcomes, but further efforts to optimize implementation are required if their true potential is to be realized.