This study examined the effects of an intensive remedial program, Wilson Reading System (WRS), on 43 struggling readers from second to twelfth grade. The students, who attended a large southwestern urban school district, were all at least two grade levels below their peers in reading. Participants received 20 hours of WRS instruction over the course of one month as part of a WRS teacher certification course. Using the Woodcock-Johnson III Tests of Achievement, students were evaluated prior to and following their participation in the intensive summer program using five subtests (Letter-Word Identification, Reading Fluency, Spelling, Word Attack, and Spelling of Sounds) and two clusters (Basic Reading and Phoneme/Grapheme Knowledge) to assess gains in students' reading achievement. Since the intervention was delivered for such a brief period, this study was designed to provide a snapshot measure of initial reading skill gains. While a failure to perform significantly better was observed on the Letter-Word Identification, Reading Fluency, and Spelling subtests, students demonstrated significant improvement on Word Attack and Spelling of Sounds subtests following WRS instruction. Furthermore, students significantly improved on the Basic Reading and Phoneme/Grapheme Knowledge clusters. Study limitations and implications for future research and practice are discussed.