Purpose: The purpose of this journal-ready dissertation was to determine the degree to which ethnicity/race and economic status of Texas Grade 3 students is related to their mathematics achievement. In the first study, the degree to which ethnic/racial (i.e., Asian, White, Hispanic, Black) differences might be present in the mathematics achievement of Texas Grade 3 students was examined. In the second study, the extent to which economic status (i.e., Poor and Not Poor) is related to the mathematics achievement of Texas Grade 3 Black and Hispanic boys was addressed. In the third study, the degree to which economic (i.e., Poor and Not Poor) differences might be present in the mathematics achievement of Texas Grade 3 Black and Hispanic girls was determined. In all three studies, analyses were performed to determine if any trends are present in the reporting categories and performance levels across three school years (i.e., 2016-2017, 2017-2018, 2018-2019) by the ethnicity/race and economic status of Texas Grade 3 students on the state-mandated mathematics assessment. Method: For these quantitative analyses, a causal-comparative research design was utilized. Texas statewide archival data from the State of Texas Assessment of Academic Readiness (STAAR) Mathematics assessment for Grade 3 students were requested and obtained from the Texas Education Agency Public Education Information Management System for the 2016-2017, 2017-2018, and 2018-2019 school years. Findings: Regarding ethnicity/race, a clear stair-step effect was present in that Asian students had the highest mathematics test scores, followed by White students, Hispanic students, and Black students had the lowest mathematics test scores. Concerning economic status, Hispanic and Black boys who were Poor had statistically significantly lower mathematics test scores than Hispanic and Black boys who were Not Poor. With respect to girls of color, Hispanic and Black girls who were Poor had statistically significantly lower mathematics test scores than Hispanic and Black girls who were Not Poor. Results for all three school years and for all three articles were congruent with the existing research literature. Recommendations for future research and implications for policy and practice were provided. [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.]