This study examined attributes of self-directed learning (SDL) in students, grades 8 through 12, taking online courses through a state-wide online program in the Southeastern United States. The study investigated whether distinct latent classes of SDL exist; whether there was a significant difference in SDL according to gender, ethnicity, and grade level; and whether significantly different online course completion, online final grade, or GPA were associated with SDL class membership. Existing data from 780 enrollments included masked demographic and achievement data, and responses to the 12-item Self-directed Learning Inventory (SDLI) with responses based on a five-point Likert scale. The SDLI used in this study was modified from the original 10-item version (Lounsbury, Levy, Park, Gibson, & Smith, 2009). Psychometric analysis based on item response theory resulted in selection of nine items from the original SDLI and one of the new items to generate measures of SDL from the item responses. SDL scale score calculations based on Samejima's (1969) graded response model were used in latent class analysis resulting in the three latent class model for SDL used in subsequent statistical analyses when addressing the research questions. Results of inferential statistics support the premise that statistically different latent classes of SDL do exist within the population of online secondary students, and that there is a correlation between self-directed learning and academic achievement. Results of this analysis indicate that there is no significant difference in SDL according to gender or ethnicity. While SDL is statistically different by grade level, the effect size is very small. The completion of online courses associated with self-directed learning class membership was significantly different by SDL class membership. Although there was a significant difference in academic achievement as expressed by final online course grades, the effect size indicated no practical significance. There was also a significant difference in academic achievement as expressed by GPA. This result may lend itself to practical application for online secondary schools. Recommendations for further study included repetition of the study with urban students and over several terms. [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.]