The purpose of this study was to explore high school students' and teachers' experiences and perceptions of effective online learning compared to a face-to-face learning environment. A great deal of evidence exists showing that no significant difference should be expected regarding a well-designed online learning environment compared with well-designed in-person learning environment (Clark, 1983). Significant differences still exist in the way students perceive their online experiences during learning (Paul & Jefferson, 2019). Districts offer online courses because it is considered to be more cost-effective. For example, online courses allow districts to eliminate the need for additional physical space (Krafcik 2010; Olster, 2010). This was a mixed methods study that included a single subject case study that examined the experiences and perceptions of one high school teacher. Data instruments include a student survey using a 5-point Likert Scale that measures teacher presence, social presence, and cognitive presence. A teacher survey consisted of ten open-ended questions on the planning and delivery of the online course and traditional face-to-face course. The survey aligns with student responses from interviews and focus group discussions. The researcher was the primary instrument for data collection and analysis. This study pointed out important differences in the student-teacher relationship between online and face-to-face instruction. It was concluded that important differences between the two modalities were found regarding the teachers' perceptions of the students and regarding ways that the teacher and students communicated. These findings deepen the understanding of the teacher-student relationship in online learning, as compared to face-to-face learning. These findings could assist in thinking of ways to promote better student-teacher relationships in online teaching. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]