Within most models of multi-tiered systems of support, Tier 3 supports are the most intensive supports public schools can provide to their students. These supports may be delivered to address academic, behavioral, or mental health concerns. Because many schools do not have the mental health personnel to effectively deliver Tier 3 mental health supports to students, community-based mental health programs have been integrated into public schools in some districts to provide more intensive services to youth within the school setting. The goal of bringing Tier 3 mental health supports into schools is to address the mental health needs of students with the greatest level of need, and ultimately, support effective schooling and education (Atkins et al., 2010). Although many schools work with community agencies to provide Tier 3 support to students, there is very little research examining the effectiveness of Tier 3 supports and their relationship to grade point average (GPA). The main goal of this study, therefore, was to investigate whether Tier 3 mental health services provided by a community-based agency in a high school setting influenced the GPA of students receiving these services. It was hypothesized that the students who received services would evidence increased academic success as measured by GPA. This study also aimed to evaluate the relationship between the number of sessions attended and the difference between pre and post-GPA. It was hypothesized that there would be a relationship between sessions attended and the difference between pre and post-GPA. Data from 40 students who received Tier 3 mental health interventions from a community agency in one high school in a northeastern state of the U.S. were analyzed. Contrary to expectations, results showed that neither of the variables of interest (GPA and sessions attended) were statistically significant in this study. Rather, GPA prior to treatment (pre-GPA) was by far the best predictor of academic performance post-treatment (post-GPA). [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]