District-level implementation of British Columbia's school food and beverage sales policy: a realist evaluation exploring intervention mechanisms in urban and rural contexts.

Intervention: British Columbia's (BC) provincial school food and beverage sales policy.

Research Question: What are the processes associated with district-level implementation of BC's school food and beverage sales policy?

Methods: We adopted a realist approach and a qualitative, multiple case study design that included three urban and two rural BC school districts. Data collection involved semi-structured interviews and questionnaires with health, education, and industry stakeholders, observations, document analysis and website scans. Analysis identified: (i) mechanisms influencing if and how stakeholders engage in implementation activities at the district level and (ii) specific dimensions of context influencing these mechanisms.

Results: We identified three mechanisms driving implementation processes at the school district level associated with BC's school food and beverage sales policy. These mechanisms are influenced by various dimensions of context that lead to a range of implementation outcomes. The 'mandatory mechanism' refers to the mandatory nature of the policy effectively triggering implementation efforts, influenced by a normative acceptance of the education system hierarchy. The 'money mechanism' refers to how this district demand leads vendors to create a compliant supply; it is influenced by beliefs about children's food preferences, health and food, and the existence of competition. Finally, the 'monitoring mechanism' refers to how systems of informal monitoring are used to promote compliance in the context of a competitive sales environment.

Conclusion: The outcomes of these three policy mechanisms are influenced by complex dimensions of context. Identifying context-mechanism interactions can help inform public health policymakers interested in interventions for improving school food environments.