The purpose of this study was to determine if there is a statistically significant mean difference in math and reading student performance by types of schools. The types of schools were identified as all-male and all-female public middle schools. Specifically, this study examined the impact of public single-sex schools on the mathematics and reading performance of seventh grade middle school students based upon the state assessment, the Texas Assessment of Knowledge and Skills (TAKS). The two performance level descriptors for the TAKS, Met Standard and Commended Performance were investigated. An ex post facto (causal comparative research) design was employed in the study. The population of this study consisted of 542 seventh grade students enrolled in four public single-sex middle schools (2 female and 2 male) in three urban school districts. Three hundred twenty-one (321) seventh grade students in 2009 and two hundred twenty-one (221) students in 2010 participated in the present investigation. Descriptive data were computed on the seventh grade students by gender. The One-Way MANOVA was conducted to determine the effect of single-sex schools on student performance. The findings (met standard) revealed that the combined TAKS mathematics and reading scores of seventh grade students were significantly affected by both the all-male and all-female schools. Moreover, it is interesting to note from the study that female students consistently outperformed their male counterparts in both reading and mathematics over both academic years. In regards to the impact of single-sex schools on commended performance, the data indicated that single-sex schools did not produce a significant effect on the combined TAKS commended mathematics and reading scores. The results showed that for 2009, there was no statistically significant difference in commended math and reading scores by type of school. However, in 2010, there was a statistically significant difference in commended reading scores for girls in that they scored substantially higher than their male peers. In summary, during both academic years, middle school female students who attended single-sex schools performed significantly better on the mathematics and reading sections of the TAKS in comparison to their male counterparts who attended single-sex schools. In regards to commended performance, in 2009 there was no significant difference between male and female students who attended single-sex schools. However, in 2010 there was a significant difference observed and female students performed significantly better on the reading section of the TAKS. [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.]