This report presents exploratory impact findings for 3-year-olds from the Head Start CARES demonstration, a large-scale randomized controlled trial implemented in Head Start centers for one academic year across the country. The goal was to test the effects of three distinct classroom-based program "enhancements" for improving children's social-emotional competencies. The Incredible Years Teacher Training Program supports children's ability to regulate their behavior by helping teachers maintain an organized classroom. Preschool PATHS uses structured lessons to help children learn about emotions and gain social problem-solving skills. Tools of the Mind-Play, a one-year program adapted from the original two-year Tools of the Mind program, promotes children's self-regulatory skills through structured make-believe play. (author abstract)