America's public schools have faced challenges in educating students, particularly those identified as at risk. According to the No Child Left Behind Act, nearly 70% of 4th grade students are unable to perform on a basic level on national reading tests. The research problem in this study addressed the significance of guided reading instruction, based on Vygotsky's zone of proximal development theory, on 4th grade at-risk students at one southeastern Title I school. The purpose of this quantitative study was to determine if there was a significant difference in reading comprehension and reading attitudes of at-risk students before and after participating in guided reading instruction. The research questions addressed the significance of guided reading instruction on at-risk students. A quasi-experimental single-group interrupted time-series design was used to record baseline data, pre-intervention data, and post-intervention data, for a group of 43 at-risk students. Data were collected and analyzed by conducting repeated-measures ANOVAs and calculating the means and standard deviations of the STAR Reading scores and Elementary Reading Attitude Survey results. The results showed no significant differences before and after participating in guided reading instruction. This study contributes to positive social change by suggesting that educators closely monitor the effects of guided reading and recommending that educators implement effective reading strategies for their at-risk student populations, thus preventing at-risk students of today from becoming at-risk adults of tomorrow. [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.]