Purpose: The purpose of this study was to explore the perceptions of master teachers, administrators, and teacher trainers about the content of Student Evaluations of Teachers (SET) in California high schools. This study also sought to reach a consensus among experts concerning how SETs can be used both in teacher evaluations and in professional development practices and content at the secondary level. Methodology: A classical Delphi method was utilized to collect perceptual data from a panel of California master teachers, administrators, and teacher trainers that met specific criteria regarding their education, involvement in their professional communities, and their role training of new and experienced teachers. For the purposes of this Delphi study, an electronic questionnaire was distributed in three rounds to assess the participants' perceptions of the content and use of SETs to inform evaluation and professional development practices. Findings: Analysis of the mixed methods data indicated a variety of findings. First, a collection of forty-nine potential SET questions were generated and ranked. Next, participants favored using SETs at the secondary level for informing professional development purposes over using them as a weighted factor in teacher evaluations. They also gave higher rankings to questions that addressed a teacher's actions and affect in the classroom over those that dealt with course content and activities. Finally, preference was expressed for twice-yearly implementation, with the resulting data being distributed individually and in aggregated form for subject leads and administrators. Conclusions: This study supported the use of SETs at the secondary level, particularly to inform professional development processes. It also revealed continued resistance to the use of SETs in teacher evaluations, in part due to the perception that secondary students' biases would influence their ratings. Recommendations: Further research is recommended to explore the effects of teacher unions on SET acceptance and implementation, the possibility of using SETs with younger students, the effects of SET implementation on student voice, and the potential sources of professional development once specific needs are identified through SET use. [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.]