Teachers' patterns of implementation of an evidence-based intervention and their impact on student outcomes: results from a nationwide dissemination over 24-months follow-up.

More information is needed about factors influencing real-life implementation and program impact of interventions effective in controlled study conditions. Ongoing national implementation of an evidence-based HIV prevention program targeting grade 6 students in The Bahamas offers the opportunity to examine patterns of implementation and relate them to student outcomes. Data were collected from 208 grade 6 teachers, 75 grade 7 teachers and 4411 grade 6 students followed over 2 years. Mixed-effects modeling analysis examined the association of teachers' patterns of implementation with student outcomes. High quality program implementation in grade 6 (high implementation dosage and fidelity) was significantly related to student outcomes six and 18 months post-intervention. Quality of implementation of the booster session in grade 7 was also significantly related to student outcomes in grade 7. Quality of delivery of the brief booster session a year after initial implementation is important in maintaining or resetting the student outcome trajectory.