The purpose of this study was to investigate the impact of a reading intervention program used with second and third grade students identified as not meeting grade level expectancy. Studies have indicated students who are not reading at grade level by the end of the third grade have an increasingly difficult time achieving at the rate of their same-age peers. In this mixed-methods case study, the researcher analyzed end of the year report card data for 30 students who received reading intervention using the Rigby Intervention By Design Program, conducted a Content Knowledge Survey with teachers, and performed Literacy Walkthroughs to determine level of program implementation. The Rigby Intervention By Design program is a component of a core-reading program designed to provide teachers the tools for intervening with below-level readers focused on the five pillars of reading instruction: phonics, phonemic awareness, vocabulary, comprehension, and fluency. The research questions in this study included 1) In what ways will teachers' beliefs and perceptions about the Rigby Intervention By Design Program affect the achievement of students who are reading below grade level or students struggling with specific reading skills by the end of the academic year, and 2) In what ways will the implementation of the Rigby Intervention By Design program affect achievement of students who are reading below grade level or students struggling with specific reading skills by the end of the academic year? Findings from the achievement data of the 30 students receiving the intervention program did not show a statistical difference in the number of students increasing or maintaining reading ability before and after the intervention. Furthermore, teachers participating in the Content Knowledge Survey expressed inconsistent feelings about the effectiveness of the Rigby Intervention By Design program and the impact on reading instruction. However, literacy walkthrough data demonstrated most teachers to demonstrate high levels of program implementation. As a result of the findings, educators may be better prepared to help students with reading difficulties through an understanding of the assistance that these children and their teachers need. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]