Studies indicate that socio-emotional-focused interventions can create lasting benefits for children across a variety of domains. Primary Project is an evidence-based program established 60 years ago that has historically been found to help improve children's social and emotional skills. The present study analyzed its continued effectiveness as well as explored factors that may mediate its efficacy. Teacher-Child Rating Scales (TCRS) for 504 children ages six to eight-years-old were analyzed using a Wilcoxon signed ranked test, and a three-way mixed ANOVA. The results indicated that participants' scores increased across all four domains: task orientation, behavior control, assertiveness, and peer social skills. Of the four domains, participant's task orientation and assertiveness scores increased the most. The study found a two-way interaction between time and age but no two-way interaction between time and gender. The clinical implications of this study indicated that Primary Project is effective for a large subset of children. The study also implied that Primary Project was useful across both genders in improving social-emotional skills. Results in the study suggest that broader use of Primary Project across different schools may be beneficial in enhancing social-emotional skills for at-risk children. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]