This quantitative non-experimental study was conducted to determine the effectiveness of Istation, a computer-assisted instruction program, as a form of intervention to improve students' overall reading ability score after use for three consecutive full years (2012-2013, 2013-2014, 2014-2015). Achievement was measured by Istation's Indicators of Progress (ISIP) Early Reading that monitors and assesses students based on the ability index that places them in Tiers 1, 2, and 3. Also, students' ethnic groups (White, Hispanic, or African American), English as Second Language (ESL) status, and socioeconomic status (free or reduced-price meals eligibility) were examined to assess whether these variables, in combination with end of the year (EOY) ISIP Early Reading scores at Grades 1 and 2, explained the variance of students' overall reading ability score at the end of Grade 3. Furthermore, this study was conducted to determine how much variance of the students' Grade 3 State of Texas Assessment of Academic Readiness (STAAR) reading scale scores can be explained by their overall reading ability assessed by ISIP. In the North Texas suburban district, the elementary school that was studied has used Istation as CAI and ISIP Early Reading as an online CAT program in kindergarten through Grade 3 since 2011. The use of multiple regression was appropriate to examine the influence of student demographic variables (ethnicity, ESL status, and socioeconomic status) and Grades 1 and 2 ability scores on the Grade 3 ability score. The researcher used simple regression analysis to examine how much variance of the students' Grade 3 State of Texas Assessment of Academic Readiness (STAAR) reading scale scores can be explained by their overall reading ability assessed by ISIP. Of the variables analyzed, students' demographics did not explain the variance of student Grade 3 EOY ability index scores, but the students' past overall reading abilities in Grade 1 and 2 did explain the variance of student Grade 3 EOY ability index scores. However, students' overall reading abilities on ISIP in Grades 1 and 2 explained the variance of student performance on STAAR in Grade 3. Findings of this study support the significance of early reading intervention and effective classroom reading instruction integration with Istation as a form of supplemental reading intervention. Therefore, district and campus administrators may examine the appropriate future usage of Istation. [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.]