The purpose of this quantitative quasi-experimental study was to identify to what extent professional development impacts student achievement in reading. The model of professional development investigated within this study was Instructional Coaching. Student reading scores from third, fourth, and fifth grade classrooms whose teachers received the treatment of instructional coaching were analyzed. The dependent variable used to measure to what extent that the independent variable had an effect on student achievement was the nationally normed reading assessment AIMSweb Reading Curriculum Based Measure. The use of a t-test was the primary statistical analysis conducted. Results determinant of whether or not mean scores in reading were significantly different across pretest and posttest scores were reported at a 0.05 probability level. Results denoted that there was a statistically significant difference in student reading scores from pretest to posttest that could possibly be attributed to instructional coaching. A calculation of effect size quantifying the size of the difference between pretest and posttest scores served as the secondary statistical analysis. Results from the calculation of effect size indicated that the intervention of instructional coaching had a substantial effect on student achievement d=0.94 as compared to an effect size of d=0.56 calculated from the control group. The use of a Chi-Square Goodness of Fit test and an Analysis of Covariance provided that the average rate of improvement (ROI) for students identified as performing at and below the 25th percentile in fluency whose teachers received instructional coaching was found to be equivalent to that of students performing above the 50th percentile as reported by the national average. Further research should focus on an expansion of these preliminary findings in measuring the effectiveness of professional development models against student achievement.