This study was conducted to determine if differentiated instruction improved student growth. The overall effectiveness was studied as well as that of gender and the aptitude of average and above average students. The study was that of a quasi-experimental design using student subjects in the classrooms of three second-grade teachers. The school in the study was located in an affluent suburb outside of a major city in the Midwest. This quantitative study concluded that differentiated instruction did not have an overall effectiveness at a significant level. Students with a higher academic ability benefited significantly with opportunity to be challenged at a higher level while students of average ability did not. There was no significant difference between the achievement of males and females. [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.]