A multi-site study of implementing a school-based health promotion intervention in Sweden - changes in readiness and implementation outcomes.

BACKGROUND: Schools are a key setting for child health promotion, yet implementing school-based programs, particularly those involving parents, remains challenging. Organizational readiness and early implementation outcomes, acceptability (ACC), appropriateness (APP), and feasibility (FEAS), capture how stakeholders perceive the implementability of new interventions and engage with them. These perceptions may evolve during implementation, but evidence on how they change over time and relate to one another in real-world school settings is limited. This study examined these changes among school staff during the first year of implementing the Healthy School Start program in schools in three Swedish municipalities (M). METHODS: Validated questionnaires were used to assess readiness, ACC, APP, and FEAS pre- and post-intervention to examine how these implementation variables varied with direct experience of the intervention. Data were collected from 39 school principals, 72 teachers, and 40 school nurses between September 2021 and June 2023. Multilevel linear regression models with random intercepts for school and individual examined pre-post changes and interactions by municipality and professional group. RESULTS: Readiness, ACC, and APP declined significantly from pre- to post-intervention in the total sample (readiness: β = -2.54, p = 0.032; ACC: β = -1.31, p = 0.004; APP: β = -1.12, p = 0.022), while FEAS remained stable (β = -0.30, p = 0.501). M2 schools reported lower baseline scores than M1 schools on ACC, APP, and FEAS. M1 schools showed significant declines across all four outcomes, while M3 schools remained stable. FEAS was the only outcome for which pre-post change differed significantly across municipalities (time × municipality interaction: χ²(2) = 9.56, p = 0.008), driven by a decline in M1. No significant differences were observed between professional groups, although school nurses reported the lowest readiness and feasibility scores. Baseline readiness was strongly correlated with ACC (ρ = 0.66), APP (ρ = 0.67), and FEAS (ρ = 0.73; all p < 0.001). CONCLUSION: Perceptions of implementability generally declined with feasibility remaining stable overall except for one municipality showing a significant decline. These findings run counter to assumptions that exposure alone improves implementation outcomes, and suggest that perceptions are shaped by organizational context, underscoring the importance of addressing contextual barriers both before and during implementation. TRIAL REGISTRATION: Registered prospectively at ClinicalTrials.gov ID: NCT04984421, registered July 30, 2021.