In this study, the researcher examined the idea of the Catholic School Advantage (CSA), whether it is a quantifiable effect, or if it can be explained by selection bias on the part of parents. Additionally, the researcher sought to examine if this selection bias, if it exists, could explain any academic achievement differences between Catholic schools and private schools. Analysis used included ANOVA, chi-square, and multinomial logistic regression to investigate selection bias and compare academic outcomes between Catholic schools (CS), other religious (OR) schools, and private schools (PS). Analyses revealed no significant evidence of selection bias among CS, OR schools, or PS. No significant academic advantage was found among the three types of schools as well. Correlations were found between age of Kindergarten entry and the selection of OR schools or PS, and socioeconomic status and PS. No evidence of an academic CSA was established. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]