This document summarizes Holly Petrich's research on defining teacher quality from the perspectives of administrators, teachers, and students. Surveys were sent to administrators, teachers, and high school students in Minnesota to gather their views. Administrators and teachers ranked challenging students academically and student achievement as top indicators of quality, while students prioritized preparation, patience, and making classes interesting. Interviews found administrators and teachers saw the link between relationships and achievement, while students valued clear explanations and practice time. The research suggests teacher quality is the most important school-based factor for student achievement.