In this dissertation study, we investigated professional learning practices common to tiered systems, with specific focus on the Comprehensive, Integrated, Three-Tiered (Ci3T) model of prevention. First, we outlined tiered models and how they address the rising, multiple needs of students, and the fitness of Ci3T for the current educational landscape (i.e., Ci3T addresses students' academic, behavior, and social and emotional well-being learning needs in one integrated model). We highlighted practice-based professional learning as one mechanism to deliver high-quality professional learning and highlighted the importance of assessment of adult learning outcomes to ensure teachers have garnered necessary skills to implement tiered models with success. (Chapter 1). Then, we conducted a literature review to map the professional learning literature of prevention and response efforts common to tiered models. We noted the gap in the literature of reporting adult learning outcomes from professional learning (Chapter 2). Next, we described the method we developed to examine: (1) participants' professional learning outcomes; and (2) their views of the Ci3T Professional Learning Series (Lane et al., 2019). Moreover, we extended the work Lane and colleagues (2020) to determine if participants' learning outcomes in this study were similar, when professional learning efforts were led primarily by district-level professionals. We examined the extent to which participants gained perceived knowledge, confidence, and usefulness as well as actual knowledge from pre-training to post-training. Next, we inspected relations between perceived and actual knowledge, replicating the perceived and actual knowledge analysis featured in Lane et al. (2020). We extended to examine differences in these professional learning outcomes across two cohorts. Lastly, we explored data from a series evaluation to note participants' evaluation of the professional learning series. We analyzed this data for the overall sample and conducted a comparison between cohorts (Chapter 3). Results indicated all educators demonstrated positive changes in knowledge, confidence, and usefulness over the course of the Ci3T Professional Learning Series, with no statistically significant differences between cohorts. Additionally, actual and perceived knowledge scores maintained notable differences between constructs at pre-training and post-training. Finally, educators evaluated the series positively, with little differences between cohorts. Then, we discussed results, including educational implications, limitations, and directions for future research. We encourage trainers and coaches of future Ci3T Professional Learnings to adhere to the manualized training as doing so will likely result in similar outcomes (e.g., significant increases across all constructs for all participants) and to reassess learning outcomes once participants are implementing Ci3T to continue to gauge progress toward mastery and inform professional learning efforts. We note limitations of the design, homogenous sample of participants, and limited scope of the study. Thus, we recommend future research incorporating the following: control groups (e.g., RCT) to determine causal relations between training and learning outcomes, samples representing a diverse pool of educators (e.g., race, geography, level of education, role), and studies including outcomes of training and implementation covering multiple years of interacting with Ci3T content (Chapter 5). [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.]