Pilot multimethod trial of a school-ethos intervention to reduce substance use: building hypotheses about upstream pathways to prevention.

Purpose: Interventions to improve school ethos can reduce substance use but "upstream" causal pathways relating to implementation and school-level changes are uncertain. We use qualitative and quantitative data from a pilot trial to build hypotheses regarding these.

Methods: The Healthy School Ethos intervention involved two schools being provided with facilitation, training, and funding to plan and implement actions (some mandatory and some locally determined) to improve school ethos over one year.