This article reports an evaluation of a reading remediation program delivered to 151 high-risk students in a public school setting. Implementation fidelity was assessed by the amount of time each child was exposed to the program. Despite receiving fewer than the recommended hours of instruction, analyses of standard achievement scores indicated significantly greater change than expected in reading comprehension, reading fluency, and word attack skills. Number of individual hours of instruction yielded the most conservative estimates of change across time. Findings are discussed within the context of conducting effectiveness evaluations of educational interventions and the need to monitor implementation fidelity at the individual level to best inform decision making and resource allocation. (Contains 5 tables.)