Although the Fast Track intervention successfully reduced the aggression levels of youth in elementary school (CPPRG 2002) and also reduced juvenile arrests and conduct disorder (among the highest risk youth) (CPPRG 2010b, 2011), the present study found no evidence that it delayed the timing of sexual debut, significantly reduced pregnancy or STDs through age 17, or moved youth from higher-risk to lower-risk profiles of tri-morbidity. It is valuable to speculate about the possible reasons for the lack of significant intervention effects. The expectation that Fast Track might reduce risky sexual activity was based upon a developmental model in which child aggression at school entry contributes to a negative cascade, fueling interpersonal conflict (with teachers, peers, and parents) and learning failures that undermine social control and school engagement. By the end of elementary school, alienated and disengaged aggressive youth are vulnerable to the attractions of a deviant life-style that offers easy social affiliation and gratification (e.g., substance use, sexual activity) and allows them to escape from restrictive (often punitive) school demands and behavioral controls (Capaldi et al. 1996; Schofield et al.
