The purpose of this study is to determine if and to what extent disparities in the referral of student subpopulations for discretionary discipline exist and if changes in disparity correlate with changes in campus academic achievement. In this study, 31 million observations of discipline data generated by reason code 21, violations of the student code of conduct, over 20 years in Texas secondary (grades 6-12) public schools were examined. Using a risk ratio to describe the likelihood that students from a subpopulation would receive a code 21 referral, an index was calculated by subtracting the smallest non-zero risk ratio for each subpopulation from the largest in each year to measure the size of disparity. The trend in disparity was then examined at the state level over time. Then at the campus level, the index was correlated to the percentage of students meeting the minimum standard on Texas accountability assessments using simple, partial, and semipartial correlations. This study found that disparities in secondary discretionary discipline do exist in Texas between the 1999-2000 and 2019-2020 school years. On average, 9.33% of 5,220,197 secondary students receive a code 21 over the course of a school year. However, 15.22% of Black or African American secondary students and 7.41% of White secondary students receive a code 21 in the average year. The trend for indices increased in the first decade and then decreased after the 2009-2010 school year at the state level. At the secondary campus level, disparities are negatively correlated (r = -0.1301) with the campus percentage of students who pass Texas accountability assessments. This correlation is weak because it only explains about 1.7% of the variance (r[superscript 2] = 0.0169). The higher the disparity in discretionary discipline, the lower the campus passing rate tends to be over time; however, this does not mean that rising levels of disparity cause campus passing rates to decline. The annual campus level correlations were weakest in 2000 at -0.0060 and strongest in 2016 at - 0.2002. In the final year under study, 2019, the correlation was -0.1709. This increasingly negative correlation is evidence that the strength of the relationship between disparities in discretionary discipline and campus passing rates has increased over the last two decades. [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.]