Dual-enrollment programs allow high school students to enroll in college-level classes to gain college and high school credit concurrently. Research on how online, dual-enrolled high school students (DES) construct knowledge when compared with online community college students (CCS) is needed to help administrators determine the design, implementation, and support systems that maximize dual-enrolled students' program outcomes. Using the Community of Inquiry (CoI) framework, the purpose of this mixed methods case study was to analyze, compare, and contrast the characteristics of knowledge construction for CCS and DES in an online, undergraduate Midwestern college sociology course by exploring knowledge construction patterns and determining how they were similar and different across the three elements of CoI (social, teaching, and cognitive presence). Data sources were archived course discussion transcripts, a teacher interview, the class syllabus, and podcasts. Qualitative themes were derived using a combination of framework categories and open coding. The CoI model was used to transform the data quantitatively, and t tests and Pearson correlation coefficients were used for comparisons. Findings included: (a) the CoI model can be applied to high school level students, (b) DES used discussion as an academic growth platform while CCS struggled with the same, and (c) metacognition may be a 4th contributor in the model. Recommendations include integrating the groups, which may offer greater academic rigor and high-quality academic modeling opportunities for both. Positive social change implications include providing insights that allow administrators to enhance offerings for dual-enrollment students and resulting student success in academia and lifelong learning. [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.]