This current study explored outcomes of SEL competencies including self-efficacy toward classroom performance, emotion regulation, stress, and the use of breathing and mindfulness strategies after implementing SEL-based yoga programming among youth Grades 3 through 5 (N=403). Findings indicate that SEL-based yoga programs support stress reduction and SEL competencies, specifically self-efficacy toward classroom performance and emotion regulation among youth. Tools such as mindfulness and breathing strategies were found to support students regardless of participation in the treatment or control group. Furthermore, it was discovered that the use of breathing and mindfulness strategies was a significant predictor of students' self-efficacy toward classroom performance among students who reported having high levels of stress, p < 0.05. Likewise, breathing and mindfulness strategies supported students having low levels of stress in emotion regulation outcomes, p < 0.05. Future interventions should align SEL program goals and measurement tools and explore more specifically what mindfulness and breathing strategies students are utilizing for stress management. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]