The primary focus of RtI has been at the elementary school level. However, over the past few years there has been a shift, and RtI has been expanding to secondary schools. Through this expansion, it is unclear if RtI has been effectively implemented at the secondary level. The ultimate goal for any school implementing change is institutionalization or sustainability. Therefore, this qualitative case study examined the institutionalization or sustainability of RtI systems in one high school. This study was designed to deepen the understanding of secondary RtI and to add to the literature on RtI at the secondary level. The purpose was to understand how one secondary school addressed the complexity and uniqueness of the secondary environment while sustaining RtI practices. The participants in this study shared several research-based practices that they believed assisted struggling students to become academically successful. The findings regarding RtI practices and implementation were supported by researchers whose works were analyzed in the literature review. The study concluded that understanding the phases of change, the three major forces which influenced change and a clear, well thought out plan are vital components to success.