Unraveling the "black box" of school tobacco policy implementation: A mixed-methods study at Danish vocational schools informed by Normalization Process Theory.

Background: Smoke-free policies are often poorly implemented in schools. The Smoke-Free Vocational Schools intervention aimed to support the routine implementation of a comprehensive school tobacco policy at Danish vocational schools and took place across seven schools. This study aimed to assess and understand the mechanisms-that is, reasoning and behavior change-that shaped if and how policy implementation outcomes occurred. Method: We applied a convergent mixed-methods design informed by Normalization Process Theory (NPT). The quantitative strand employed a repeated cross-sectional design, assessing implementation mechanisms-Coherence, Cognitive Participation, Collective Action, Reflexive Monitoring-and implementation outcomes at two time points: 5+ months post-policy (T1) and 14+ months post-policy (T2). Additional mechanisms-Change Commitment and Change Efficacy-were surveyed among subsamples who completed questionnaires pre-policy (T0) and at the follow-ups (i.e., T0-T1 and T0-T2). The qualitative strand involved interviews and focus groups with 40 participants to explore the mechanisms and their connections to intervention activities. Integration of qualitative and quantitative findings was achieved through joint displays. Results: Quantitative analyses included responses from Conclusions: This study identified critical mechanisms for implementing school tobacco policies and demonstrated how specific intervention activities can activate these mechanisms, offering guidance for future research and practice development.