This study explores the role of high school students' perceptions of teacher understanding in the development of caring student-teacher relationships. Whereas past research has embedded understanding as a facet of care, this research distinguishes between care and understanding to examine whether and how understanding is necessary for care. Extending Noddings' (1992) conceptions of "caring as virtue" and "caring as relation" to consider "understanding as virtue" and "understanding as relation," the researchers analyzed 33 interviews with high school students discussing 65 student-teacher relationships to consider the nuances within these different types of relationships. The findings confirm that caring as relation is the more desirable form of teacher care and that in most instances of relational caring, students perceive that teachers understand them both as people and learners. However, this is not uniformly the case, and many students perceive agency in co-creating their relationships with teachers by regulating the extent to which they allow teachers to understand them. The researchers recommend greater attention to the development of understanding as virtue within high schools as a middle ground between a complete lack of understanding and extensive relational understanding. This research has implications for teachers and school leaders seeking to foster stronger student-teacher relationships.