A current trend in public schools involves the implementation of research-based interventions to address the needs of students who are at-risk for failure. Federal legislation mandates educators to implement interventions with integrity. This study has relevance and presumed importance to educational stakeholders seeking to provide appropriate programs for struggling learners. Previous research has indicated that treatment integrity is an essential component in Response-to-Intervention (RtI) models when evaluating students to determine if they have a learning disability. However, there remains a gap in the current literature regarding treatment integrity practices among Student Support Team (SST) members. Therefore, the purpose of this study was to investigate the discrepancies between the beliefs and practices of SST members regarding treatment integrity. Intervention-Based Assessment (IBA) was the theoretical framework used for this study. The researcher conducted a sequential-explanatory, mixed-methods study in a large, urban school district in the Southeastern region of the United States. Data were collected using an online survey and focus group interview questions. Quantitative data were analyzed using descriptive statistics whereas qualitative data were analyzed using Thematic Content Analysis and Constant Comparison Analysis. The research questions for this study were designed to clarify (1) SST members' perceptions about the importance of treatment integrity and (2) the factors that impact treatment integrity efforts and the SST effectiveness. Results indicated that SSTs deemed treatment integrity to be important but did not measure it frequently due to limited resources and training opportunities. Findings suggested that the shared responsibility of providing teachers with ongoing feedback about implementing interventions with integrity could directly impact RtI and differentiated instruction, which could ultimately assist administrators with addressing the barriers to treatment integrity practice and SST effectiveness. [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.]