Consequential to the COVID-19 global pandemic, widespread school closures ensued, profoundly affecting secondary school students' academic, social, and psychological well-being. Simultaneously, the academic year of 2020-2021 witnessed a notable surge in the departure of public school teachers, with nearly half opting to resign. This exodus was primarily attributed to the heightened stress associated with virtual instruction and the inadequate provision of mental health resources for educators and students. This dissertation sought to elucidate best practices for instructional coaches collaborating with secondary school teachers to develop a comprehensive toolkit for instilling social and emotional learning competencies within classroom environments. The contagious nature of the research underscores the imperative of supporting instructional coaches, who play a pivotal role in bolstering the capacity of secondary school educators to effectively address their students' needs amidst challenging circumstances. Employing the Delphi method, the study convened a panel of experts to assess the importance of various factors identified in extant literature on SEL implementation. The findings highlighted the importance of attentive and empathetic involvement from all stakeholders, including secondary school students, teachers, and instructional coaches. These insights guided the formulation of Yarijanian's VISTA SEL Framework, customized to meet student requirements, alongside a collection of optimal strategies for instructional coaches working with secondary school teachers to promote SEL competencies within the classroom environment, as facilitated by the development of Yarijanian's MIASSIN Framework. [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.]