This study has two objectives: (1) to report the results of a large-scale, longitudinal evaluation of the WITS Programs that included a large sample of elementary school children (n = 1967) from 27 rural schools (including 16 program schools) and (2) to examine and discuss the effects of average developmental trajectories and of heterogeneity in children's development on intervention outcomes. Data comprise baseline (spring) and four follow-up assessments (5 Waves) from children (N = 1967) and their parents and teachers. WITS stands for Walk away Ignore, Talk it out, and Seek Help (www.witsprograms.com). The children in the intervention schools declined more "slowly" than those in the control schools in their reports of relational victimization. Children in the intervention schools also declined faster in aggression and emotional problems relative to children in control schools. Moderation analyses showed that intervention group children with higher baseline levels of emotional problems declined faster in emotional problems than those with lower problems at baseline. In addition, children in grades 3 and over completed school climate questionnaire and children in control schools who had more negative perceptions of school climate at baseline showed greater increases in these negative perceptions compared to children in the intervention schools. We discuss the potential impact of average trajectories of child development and the within-child heterogeneity in assessments for the interpretation of the findings. We also conclude by highlighting evaluation design modifications that may improve our future ability to examine the effects of preventive interventions for elementary school children.