The urgent need to transition rapidly to exclusively online learning environments in response to the COVID-19 pandemic presented challenges in the K-12 education system. This study sought to address the problem of the lack of exploration into the effectiveness of online learning during the COVID-19 pandemic. This quantitative study explored the effectiveness of online learning based on teachers' perspectives during the COVID-19 pandemic by comparing high school teachers' experiences with two different online learning programs, "remote" and "virtual" at a public K-12 school district in southern California, based on the existence of the three forms of presence of the CoI framework: cognitive, social, and teaching. For the purposes of this study, remote learning took place through teacher-developed online courses and virtual learning took place through vendor-developed online courses. Data were collected using the CoI survey instrument. A final sample of 96 responded to the survey (n = 72 in the remote and n = 24 in the virtual). Independent samples t-tests were performed to determine if there is a statistically significant difference in teachers' perceptions regarding the existence of the three forms of presence between the remote and virtual learning programs. Teachers in the remote reported a statistically significant higher level of agreement regarding the existence of the teaching presence and cognitive presence, and a slightly higher but not a statistically significant level of agreement regarding the existence of the social presence, than those in the virtual. These results indicate that teachers providing instruction in the remote are more likely to perceive a stronger sense of community of inquiry than teachers providing instruction in the virtual. It can be determined that when teachers design their own content, include engaging learning materials, and facilitate live interactions within their courses, they perceive higher levels of cognitive, social, and teaching presence than teachers using a pre-designed learning content developed by other educators. [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.]