Teacher collaboration is a topic that, although often studied, understanding teachers' collaborative practices continues to be complex. The study site is no exception. Recent data suggests that while collaboration among teachers is often depicted as "natural" and "easy," fostering rich and authentic collaboration can be challenging, particularly at the high school level. High school teacher collaboration has received limited attention in research compared to elementary and middle school levels, as indicated by the literature review. The study focuses on novice (Generation Z) and established (Baby Boomers, Generation X, and Millennials) teachers to explore their perspectives. Following a phenomenological approach, the study delves into the lived experiences of six novice and six established high school teachers. The study employed phenomenological data analysis of twelve interview transcripts to illuminate six essential themes across the participant responses: (a) teacher collaboration; (b) professional development; (c) time; (d) support; (e) barriers to collaboration, and (f) novice teachers' contributions to the teaching profession. Drawing on transformational leadership and adult learning theories, the study aimed to gain a better understanding of how collaboration impacts instructional practices. The findings shed light on the challenges and opportunities in fostering teacher collaboration, emphasizing the necessity for relevant and engaging professional learning opportunities. The study underscores the importance of transformational mentorship in nurturing collaborative environments where teachers can mentor and support each other's growth. By comprehending teachers' experiences, the study offers insights for developing effective collaborative practices among high school educators. [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.]