Students living in poverty are now the majority of the K-12 student population in the United States. Growing up in poverty results in lower self-regulation, executive function, and readiness to learn. Researchers suggest that mindfulness practices, such as yoga, can enhance student self-regulation and executive function, thereby increasing student readiness to learn and academic achievement. There was limited research on mindfulness practices and academic achievement as measured by standardized assessments. This quantitative descriptive comparative study of "ex post facto" data was an analysis of the 2015 Grades 3-5 New York State Testing Program English language arts (ELA) and math performance levels of a high-poverty elementary school that offered yoga to all students and a similar high-poverty elementary school that did not offer a mindfulness practice. The results of independent samples "t" tests indicated no significant difference in ELA and math performance levels between the two schools. Although results were inconclusive, this study may indicate that yoga and mindfulness practices are most effective when including or instructed by the academic classroom teacher. Limitations included the lack of longitudinal measures, no prior assessments, and no measures of fidelity of implementation. Recommendations for future studies included comparing standardized assessments of only economically disadvantaged students, using a design that incorporates pre- and posttest scores, and exploring academic achievement results based on components of the yoga or mindfulness implementations. [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/en-US/products/dissertations/individuals.shtml.]