Using a case study of three elementary schools involved in a Response to Intervention (RTI) model demonstration project, the authors examine the features critical to successful RTI implementation. Preliminary findings suggest that access to and use of sensitive progress monitoring assessments and a willingness to use the data provided by those assessments are key features of successful implementation efforts. The authors draw from a year's worth of student performance data, field observations, and interview and focus group transcripts to document both successes and challenges associated with using schoolwide RTI to close the achievement gap in reading. (Contains 3 figures.)