The notion that teacher quality impacts student achievement is widely accepted. How to best define, measure, and improve teacher quality continues to be debated by teacher unions and state legislators. Teacher evaluation studies have focused on isolated elements of the system. The purpose of this quantitative study was to examine the current teacher evaluation practices within California high schools using an instrument developed by the current study. The literature review revealed five major constructs (10 sub-constructs) based on which the instrument was developed. These constructs were (a) elements of the teacher evaluation system (contractual mandates, teacher performance measures, use of performance rubrics, and perceptions of the system), (b) classroom observation practices (pre-observation purposes and types of data collected during observations), (c) structure and frequency of the post-observation conference, (d) support for improved teacher practice, and (e) professional development of evaluation practice (type/frequency and format). Of the 1,028 possible participants, 137 administrators responded to the online questionnaire emailed to all principals at traditional, ninth through 12th grade high schools. Survey outcomes revealed that the use of a performance rubric had the highest mean among the sub-constructs measured (86%). The lowest means were types of data collected during the classroom observation (29%) and specific administrator professional development (27%). The reliability evidence of the instrument was investigated using Cronbach's alphas. Multiple regression was also employed to determine the relationship among the evaluation system elements. Results from this study have suggested that legal aspects of the system may predict practices more closely aligned to research-based practice (pre-observation conference practices and specific professional development for evaluation practice). Other practices with more research-based legal mandates were predictive of a lower practice (teacher performance measures, structure and frequency of post observation conferences and support for improved teacher practice). Further research of teacher evaluation systems using the instrument developed in this study would benefit this field of research. [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.]