This mixed-method study examined the impact of the implementation of a new multi-tiered intervention program at a private, Catholic, college preparatory high school in the Midwestern United States with a 95% Latinx population. The researchers examined the impacts of a multitiered system of support (MTSS) on various student academic achievement measures, teacher perceptions of program components associated with organizational change, and teacher perceptions of success. Fullan's (2016) educational change theory served as the theoretical framework for the current study. This mixed-method, qualitative-dominant, study included data from 14 of the 31 teachers employed full time at Midwest Private Prep and 220 of the 500 students enrolled full time during the 2020-2021, 2021-2022, and 2022-2023 school years. The quantitative results indicated statistically significantly positive results in annual student GPAs, a statistically significant decrease in student PSAT scores, and an increase in student failure rates after the implementation of the MTSS program. For the qualitative portion of the study, the research participants completed questionnaires adapted from Mortrud (2017), and teacher participants engaged in follow-up interviews. The researchers analyzed the qualitative responses using deductive themes from Fullan's educational change theory (i.e., need, clarity, complexity, and quality/practicality) and the additional theme of success from Mortrud's study. Recommendations for MPP regarding their MTSS program are 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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]