The purpose of this study was to determine how the use of www.achieve3000.com, as a computer-based supplemental English Language Art (ELA) instructional tool, affected middle school students' ELA achievement. 455 middle school ELA students from the sixth, seventh, and eighth grades participated in this study. The collected student achievement that served as variables consisted of Common Unit Assessments (CUA) gains, Tennessee Comprehensive Assessment Program (TCAP) scores, cumulative ELA grades, and Achieve3000 score averages. This study used descriptive statistics, one-way ANCOVAs to control for demographical covariates, and multiple regressions to analyze significance. The results of the ANCOVAs comparing the cohorts' CUAs, TCAP, and grades indicated no significant differences. However, the multiple regression showed a strong and significant correlation between the variables. [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.]