It is essential for educators to be able to navigate educational standards and incorporate social- emotional learning (SEL) frameworks which align with teaching practices that support students' education. Teachers may possess knowledge of SEL components, but there is currently a lack of standards, especially at the upper grade levels, in addressing how to implement these practices through lesson planning. The specific problem is that it is not known how teachers' perceptions influence their ability to integrate SEL in their teaching strategies. Teachers play an important role in developing students' SEL skills. The purpose of this qualitative case study was to investigate teachers' perceptions and knowledge regarding the factors that affect their lesson planning procedures. The conceptual framework guiding this study included The Collaborative for Academic, Social and Emotional Learning framework, and components of CASEL school theory of action model. Purposive sampling was used to recruit ten full-time regular and special education teachers, who were interviewed with open-ended questions during semi-structured interviews. To further strengthen the trustworthiness of the study, the participants also completed an anonymous online questionnaire, and prior case study research from CASEL strengthened the trustworthiness of the study. The data analysis was conducted electronically and manually with NVivo version 12. The results aligned and was supported by the previous evidence-based case studies that teachers incorporate both practical and knowledge-based pedagogy, which influences SEL in their lesson planning strategies. Future research could develop teaching practices directly associated with implementing SEL toward increasing students' knowledge and autonomy via phenomenological research, which could examine student-teacher interactions with a qualitative comparative study. [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.]