The typical mathematical experience often prioritizes achievement with little regard for the emotional disposition of the student. Despite this relentless focus, overall performance in mathematics has shown little improvement. Additionally, the surge in demand for professionals with mathematical skills highlights a concerning disparity in performance, especially among students from low-income households and communities of color (National Center for Education Statistics, 2019a). This inequality extends beyond test scores, as students of color also pursue and complete STEM degrees at lower rates than their peers (Fry et al., 2021). Despite progress in increasing female representation in STEM, women and people of color remain underrepresented in mathematics and science professions. To address these challenges, mathematics education must expand its goals to include the development of students' mathematical affect and identity, which would encourage more students to engage with and pursue careers in mathematics. The quantitative study explores the relationship between mathematical affect, identity, and academic achievement among secondary students from diverse backgrounds, with a particular focus on females and students of color. [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.]