The study was conducted to describe how third graders, teachers, and interventionists perceive the influence of a phonics treatment program on the reading achievement of third-grade students in a school in the Western United States. The study was guided by the research questions on the perceptions of students, teachers, and interventionists on the influence of explicit instruction, sequential instruction, systematic instruction, adequate modeling, corrective feedback, differentiated instruction, scaffolding, and continual assessment. The study also answered the question about the differences between the high-response and low-response students on a phonics treatment program. The sample included 18 students, three teachers, and eight interventionists from a Title 1 school. A generic descriptive design was employed where interviews, focus groups, and surveys were used as data sources. The data collected were analyzed using a thematic analysis approach. The findings indicate that the phonics treatment program and its characteristics are useful for improving students' reading literacy, enhancing skill development, and improving students' level of engagement with reading processes. The participants perceived that the phonics program enables students to improve spelling and pronunciation. Interventionists also viewed the phonics treatment program as important for skills development among the students and promoting word connections. The study further indicates that the phonics treatment program is essential because it exposes students to different teaching and learning styles for improved reading outcomes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]