This paper describes an action research project focusing on the effects of a phonics intervention on the reading fluency of high school students. Phonics instruction is normally associated with earlier stages of learners' reading development. If it is an effective tool for early readers, then it would seem that struggling readers at the high school level might benefit from an intervention program that used a phonics-based approach. Pre-testing identified the decoding skills that students were unfamiliar with and the phonics intervention addressed the identified areas of need. Students were tested three times over time: one as a baseline measure, the second after a seven-week intervention was completed, and the last one year after the completion of the initial intervention. Two measures were recorded for each of the three time spots: the first was Raw Score and the second was Reading Grade Level. Results showed that there was a significant change over time in the three measures for both Raw Score and the Reading Grade Level. All students benefited significantly from the phonics intervention. The results of this intervention encourage the use of structured phonics with struggling high school age students as a strategy to improve their reading fluency.