Instructional coaching has been implemented in schools to improve student achievement; however, literature shows a lack of evidence of the efficacy of improving student reading achievement. The problem addressed in this study was that school districts have implemented instructional coaching to improve student reading achievement, but the effectiveness was unknown. The purpose of this quantitative study was to examine the effect of instructional coaching on third-grade reading achievement. Guided by Walberg's theory of achievement, the overall research question investigated the effect of instructional coaching on third-grade reading achievement. In this quantitative, comparative study, ratio-scale data from students who received instructional coaching (intervention group) and those who did not receive instructional coaching (control group) were analyzed with a repeated-measures mixed Analysis of Variance (ANOVA). Archival data were used from the Formative Assessment System for Teachers (FAST™) on the Adaptive Reading (aReading) assessment during an 18-week instructional time for the 2018-2019 school year. The findings of this study did not show a significant difference in achievement between the control group and the intervention groups; the control group made greater gains during the instructional period than the intervention group. This study provided one step toward a better understanding for educators and school districts on the effect instructional coaching may have on reading achievement, with recommendations for additional study in this area. Studies of this type have the potential to instill positive social change for students in school districts that adopted instructional coaching to increase student achievement. [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.]