At the study site school for this research, the online curriculum in the current blended learning program was not promoting the desired student achievement outcomes. It was unknown if and how research-based best practices associated with blended learning were being implemented. This qualitative case study explored which elements of blended learning best practices were currently implemented in the online blended curriculum at one school to understand the factors enhancing or constraining student learning outcomes. A communities of inquiry framework was used to explore which blended learning best practices were currently implemented and which of those elements enhanced and constrained learning based on teacher and student perspectives. Data were collected using a whole population questionnaire, individual student/teacher interviews, and classroom observations. Three students and 5 teachers participated in the interviews and 5 classrooms were observed. Data were analyzed using a combination of open coding and a priori codes related to the conceptual framework. Findings indicated that while teacher presence was evident in the blended learning curriculum, the focus on self-paced assignments limited the social and cognitive presence needed in blended learning best practices. Results were used to design a blended learning professional development course to help prepare teachers to implement missing elements of blended learning best practices. This study can create social change by increasing teachers' understanding of blended learning and providing student learning data to help educational leaders close the achievement gap at the local site. Increasing student success could lead to lower dropout rates and enhance students' abilities to become more successful members of society. [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.]