The purpose of this quantitative observational study was to identify the differences in high school student test scores on the ACT ELA composite tests and ACT math test for students attending school in union and unified districts in Arizona. Arizona has two options for public high school districts, 9-12 (union) and K-12 (unified). The researcher looked to answer the following two questions; What is the difference in achievement level rates for proficient and above on the ACT math test for students attending union districts versus unified districts in Arizona? What is the difference in achievement level rates for proficient and above on the ACT ELA Composite for students attending union districts versus unified districts in Arizona? The theoretical framework for this research was grounded in Piaget's theory of constructivism. Piaget's theory emphasizes the role of prior knowledge in learning new content, students do not come into a class with a blank slate. Preexisting data collected from the ADE website showing ACT test results taken by public school students in April of 2023 was used. Data was analyzed to determine the total number of students tested, and the total number of students identified as proficient or highly proficient for both union and unified school districts. A two-sample z-test for proportion is utilized to compare the proportion of students labeled proficient or higher in union and unified districts. A chi-square test for independence was conducted to determine if the two variables, district type and test outcome, are independent. The data was statistically significant and both null hypotheses were rejected, concluding there is a difference in test scores for students in union versus unified districts. A longitudinal study to determine the full extent of potential differences is recommended. [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.]