This study at a public high school in the Northeastern United States explores how students’ environmental identities are affected by various activities in an Environmental Science course. Data was collected as part of an ethnographic study involving an Environmental Science teacher and her tenth–twelfth grade students. The results focus on interviews with 10 students and the teacher, conducted at three points during the semester-long course. The findings illuminate ways in which students’ identities (environmental and consumer-materialist) are affirmed or disconfirmed during classroom activities, the importance of establishing personal connections with environmental issues, and challenges related to the teaching of controversial environmental issues.