The purpose of this study was to examine the relationship between schools' multi-tiered systems of support (MTSS) implementation, students' perceptions of their social-emotional learning (SEL), educators' perception of students' SEL, and academic achievement for Hispanic/Latino, African American, and Asian elementary school students as measured by performance on the Smarter Balanced Assessment Consortium (SBAC). A nonexperimental quantitative correlational design was used for the research purpose. Panorama Education's Social Emotional Learning: Teacher Perception of Students' Social-Emotional Learning Survey was used to provide teacher perception measures of students' SEL skills. Data from the SWIFT Fidelity Integrity Assessment (FIA; SWIFT Education Center, 2013) were used to measure MTSS implementation in the school cohort identified by the participating school district. The Panorama Social-Emotional Learning: Student Competency & Well-Being Measures Survey by Panorama Education was used. Data were collected in the fall of 2022 and spring of 2023 from 5,610 grade 3 to 5 students from a school district in California. Bivariate correlations and multiple regressions were performed to answer the research questions. The findings in this study revealed that a significant relationship exists between the implementation of MTSS, SEL, and educators' perception of students' SEL. Teacher perception of students' SEL demonstrated significance for all SEL constructs. Future research is suggested to extend the examination of the MTSS framework domains as well as school district policies, procedures, and infrastructure that support fidelity of MTSS implementation at the district and site level. Future research is suggested to explore various assessment tools schools and district utilize to assess the implementation of a comprehensive MTSS. Additionally, the elementary educators' ethnicity, district demographics, and diversity influence on implementation of MTSS and SEL measures should be considered. [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.]