One middle school's implementation of corrective reading was evaluated for student reading outcomes and treatment fidelity. Findings indicated that sixth-, seventh-, and eighth-grade students made progress in decoding and oral reading fluency over the school year; however, students did not demonstrate greater gains during the semester enrolled in the corrective reading class compared to the semester they were not. Findings illustrate that a school's efforts to improve outcomes for struggling readers can be undermined without fidelity of instructional programs, highly effective teachers, and adequate professional development. Implications for supplemental reading programs at the secondary level are discussed. (Contains 5 tables.)