Purpose: The purpose of this journal-ready dissertation was to determine the degree to which the economic status and ethnicity/race of Texas Grade 4 boys and girls in special education are related to their mathematics performance on Texas state-mandated assessment. In the first article, the purpose was to ascertain the effect of the economic status (i.e., Poor and Not Poor) of boys in special education on their mathematics performance on the Texas state-mandated assessment. In the second article, the purpose was to examine the mathematics performance of Grade 4 boys in special education as a function of their ethnicity/race (i.e., Black, Hispanic, and White). In the third article, the purpose was to investigate the extent to which the economic status (i.e., Poor and Not Poor) related to the mathematics performance of Grade 4 girls in special education. In all three articles, the extent to which trends might be present in the Reporting Categories (i.e., Reporting Category I: understand numerical representations and relationships, Reporting Category II: computations and algebraic relationships, Reporting Category III: geometry and measurements, and Reporting Category IV: data analysis and personal financial literature) and mathematics performance levels: (i.e., Approaches Grade Level, Meets Grade Level, and Masters Grade Level) was examined across three school years (i.e., 2015-2016, 2016-2017, 2017-2018). Method: A causal-comparative research design was present for all three studies. Archival data were collected through a Public Information Request form for the 2015-2016, 2016-2017, and 2017-2018 school years obtained from the Texas Education Agency. Findings: Grade 4 boys in special education who were Poor had statistically significantly lower mathematics performance than their peers who were Not Poor. A clear stair-step effect existed with respect to the ethnicity/race of Grade 4 boys in special education. White boys had the highest test scores, followed by Hispanic boys. Black boys had the lowest mathematics test scores. Grade 4 girls in special education, regardless of their economic status, had similar mathematics test scores. The results for all three school years were commensurate with the existing research literature. Implications for policy and for practice, as well as recommendations for future research, 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/en-US/products/dissertations/individuals.shtml.]