This study examined the effect of kindergarten entry age on the scores of the eighth grade Comprehensive Test of Basic Skills (CTBS) math and reading scores, while controlling for the demographic variables of gender and socioeconomic status. The subjects included 1,197 students who participated in the randomized, long-term STAR (Student-Teacher Achievement Ratio) experiment. One-way and Two-way ANOVAs, as well as an independent samples t-test, were conducted to test for significant differences between group means. Ten null hypotheses were tested at the 0.05 level of significance. Results of the study indicated that there was a significant difference in eighth grade CTBS math and reading scores based on SES. There was not a significant difference in the eighth grade CTBS math and reading scores based on gender or kindergarten entry age. There was also no significant difference in the eighth grade CTBS math and reading scores based on kindergarten entry age, SES and gender combined, or age and SES combined with kindergarten entry age. [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/en-US/products/dissertations/individuals.shtml.]