The problem addressed in this study is that the low reading proficiency levels of marginalized elementary students significantly affect their future academic achievement and life outcomes. The purpose of this quantitative comparative study was to investigate the differences in the reading proficiency levels of marginalized Grade 3-5 students in a large urban school district in the mid-Atlantic after participation in the i-Ready online reading intervention program. This study involved an investigation of the variances in the efficacy of the i-Ready program on students' reading proficiency levels as measured by the beginning- and end-of-year Grade 3-5 assessments. Each of the grades' reading proficiency levels were examined and compared. Results showed Black students' reading proficiency score gains were significantly better than those of White students. There were statistically significant gains in the percentage of reading proficiency percentages for overall reading proficiency percentages. There was not a statistically significant gain in the percentage of reading proficient students for Grade 3 after participation in the training as measured by the beginning- and end-of-year assessments. Findings showed Grade 3-5 students made significant gains in reading proficiency; however, the factors influencing those gains remain unknown. The current recommendations are for students to engage in 45 minutes of i-Ready reading instruction per week. Future research should be conducted to investigate the effect of daily i-Ready reading instruction on reading proficiency outcomes. Increasing the amount of time that students receive reading instruction could have a positive effect on their reading proficiency outcomes. This type of study will inform school administrators and educators about the influence of increased i-Ready instruction time on students' reading proficiency. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]