Although reading achievement correlates highly with a student's ability to do well in school, not all children achieve in reading. The purpose of this mixed-method study was to investigate whether reading instruction provided in small groups at the child's own reading level, known as "guided reading instruction," would result in significant improvement in the reading achievement of fourth- and fifth-grade students. Teachers' commitment to and perception of guided reading instruction were also examined in the study district. The hypothesis was: Have student reading scores improved on the Illinois Standards Achievement Test (ISAT) in 2007 and 2008, after implementing guided reading instruction in the 2006-2007 school year? There were three research questions:, "Do teachers believe guided reading instruction is an effective instructional approach to improve ISAT scores? How does teacher commitment to the instructional approach affect the success of guided reading instruction? What instructional skills and strategies are required to develop an effective reading program"? Chi-square goodness-of-fit and paired-samples t tests were statistical tests employed in the quantitative portion of the study. Surveys and focus groups were used to investigate teacher commitment and perception of guided reading instruction in the qualitative portion of the study. Quantitative results indicated there is a significant correlation between guided reading instruction and improvement on ISAT scores, when students are examined over time. Qualitative results indicated teachers were committed to guided reading instruction, and perceived guided reading instruction benefitted students. Further, teachers recommended additional training in guided reading instruction, coupled with additional staff to provide guided reading instruction, would help maximize results. Preliminary results did not show significant improvement after 1 year of guided reading instruction. However, when the scores of the same students were followed over a 2-year period, significant results were noted. The most salient finding of this research reinforced the notion that the validity of any new program is onerous to judge in its inception year. Practitioners may benefit from future research that tracks the same students over an expanded period of time as well as the establishment of quality assurance measures to ensure the program continues to be administered with fidelity. [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/en-US/products/dissertations/individuals.shtml.]