 The CTC system guides community groups to choose and implement appropriate tested and effective programs, policies, and practices in families, schools, and communities (see the CTC Prevention Strategies Guide and the Blueprints for Violence Prevention website).These programs have shown significant effects on minimizing youths' risky behaviors and enhancing positive choices.The CYDS evaluated community efforts to faithfully implement (1) the core principles of the CTC prevention system, and (2) tested and effective prevention programs with respect to content and delivery specifications.