A structural model for prior achievement, school integration, and self-efficacy was developed using Tinto's theory of student attrition and Bandura's self-efficacy theory. The model was tested and revised using a sample of 1,452 males and females from single-sex and coeducational parochial high schools. Results indicated that the theoretically hypothesized model provided an adequate framework for understanding the relationships between the variables in the model. All paths were positive and statistically significant. Multigroup structural equation modeling (SEM) was then used to test and compare four groups from the sample: females from single-sex (n = 378) and coeducational schools (n = 303) and males from single-sex (n = 457) and coeducational schools (n = 314). In line with past studies, results of ANOVA tests showed mean level differences between groups on measures of prior achievement, school integration, and self-efficacy. The current study considered the limitations of ANOVA tests and also used multigroup SEM to compare groups, which allowed the relationships between variables to be tested. There was model invariance, as model fit was equal for all groups. These findings address gaps in the literature on single-sex education, which to date has been mixed and inconclusive, and provide new knowledge regarding the social cognitive processes in single-sex and coeducational schools. [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.]