The purpose of this study is to examine the relationship between virtual school size and student achievement in virtual schools in a southwestern state. Enrollment size and the following areas were studied in an attempt to determine student achievement: STAAR English Language Arts/Reading, STAAR Math, STAAR Science, and STAAR Social Studies testing scores in regards to race. This quantitative study used nonexperimental research utilizing a distribution approach. The effect of virtual school size on student achievement in a southwestern state was examined. Specifically, student achievement was defined by student passing rates on individual tests of the STAAR examination. This research was conducted utilizing archival data from TEA for 2013-2016 school years. The z-test results revealed in this study indicate students in the smaller schools performed significantly better across the three school years. The study analyzed enrollment size and STAAR English Language Arts/Reading in Grades 5 and 8, Math in Grades 5 and 8, English I, English II, and Algebra I testing scores relating to race. In all categories of both test category and race, students in smaller schools performed better than students in larger virtual schools. Notable trends were revealed in this study. First, small virtual schools outperform large virtual schools in academic achievement. Second, female students outnumber male students. Third, virtual schools are growing in demand. There was an increase in student population for all 3 school years and for all 4 virtual schools in this study. [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.]