A changing landscape in youth sports and educational institutions has resulted in a growing number of high school student-athletes being coached by adults who do not work in the schools they attend. This study provides a foundational understanding of the relationship between in-building coaches, hereafter referred to as educator-coaches, and their student-athletes. Using a generic descriptive-interpretive qualitative research (GDI-QR) approach, this study examines the unique relationship within schools and what benefits and challenges this model may provide for the mentors and mentees involved. Framed around the concepts of natural mentorship and social-emotional learning (SEL), this study highlights how the educator-coaches can foster meaningful, lasting connections with student-athletes in the school setting. Interview data were collected and transcribed through formal, semi-structured interviews with five former educator-coach and student-athlete pairs from large Illinois public high schools. Results show that the educator-coach and student-athlete relationships formed during high school fostered mentees' feelings of inclusivity, belonging, and maturity while developing traits connected to SEL, such as empathy, teamwork, and problem-solving. The foundational understanding of this mentoring relationship suggests that that educator-coaches are not only valuable assets to their schools, but their mentorship may positively contribute to student-athlete enthusiasm for attendance, confidence around academic performance, and positive social-emotional well-being in high school. [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.]