The purpose of this study was to investigate differences in high school completion rates among White, African American, and Hispanic students enrolled in different school sizes--small, medium, and large. For this causal-comparative research design, this study utilized archival data from the Texas Education Association's Academic Excellence Accountability System. The researchers utilized a convenience sample of the state's public high school students for the 2008-2009 (n = 527 schools), 2009-2010 (n = 606 schools), and 2010-2011 (n = 549 schools) school years. Two Friedman's nonparametric repeated measures analysis of variance revealed no statistically significant differences among the three groups for small and medium schools for the 2008-2009 and 2009-2010 school years. However, for large schools, statistically significant differences emerged in favor of White students for both the 2008-2009 and 2009-2010 school years, representing large and moderate effect sizes, respectively. For the 2010-2011 school year, a statistically significant difference emerged among the three groups for small, medium, and large schools, in favor of White students. Implications are discussed.