In this study, I explored how (a) a team-based instructional method rather than a one-teacher-one-classroom, traditional teaching model and (b) an inquiry-based learning approach affected teachers attitudes and self-efficacy for teaching and students attitudes, self-efficacy, engagement, and connections to school. The study was conducted within four, ninth-grade teams, composed of 3-4 teachers and about 90 students each, at a large urban, comprehensive high school in the southwest. Teacher teams were provided with professional development on using team-based techniques as well as the inquiry-based approach and formed their own communities of practice as they implemented the new instructional approach. The study was grounded in several theoretical perspectives including small learning communities, self-efficacy theory, and the question-driven inquiry framework proposed by Beagle Learning and the engineering design process. These frameworks underpinned the investigation into how inquiry-based instruction fostered problem solving and critical thinking, collaboration, and interaction, 21st-century skills, abilities consistent with the district's Portrait of a Graduate skills. In the study, I utilized a mixed-methods approach to collect quantitative and qualitative data. Quantitative results showed there were no changes in scores, but these outcomes likely were influenced by teachers and students who participated in school online during the pandemic. Qualitative data indicated students felt connected to the school, offered mixed reactions about the inquiry approach, and provided mixed comments about the team-based approach to instruction. Teacher qualitative data showed teachers viewed themselves as facilitators in the inquiry approach, embraced the community of practice they formed, and considered a teams-based approach to be motivating in their inquiry-based instructional efforts. The discussion was focused on explaining the results based on theories and previous research, lessons learned, limitations, implications for practice, and implications for research, as well as conclusions and some closing thoughts. In conclusion, this research highlighted the transformative potential of enacting inquiry-based instruction within small learning communities using a team-based instructional approach to support student development and academic achievement. [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.]