US educators express concern that students are turning away from the study of science and have little interest in pursuing science careers. Nationally, science achievement scores for 8th graders are unchanged since 1996, but 12th graders' scores have significantly decreased. A shortcoming of education reform efforts is lack of attention to students' developmental needs. Science study should enable students to learn about themselves--to develop and refine their skills, define their values, explore personal interests, and understand the importance of science to themselves and others. Effective secondary science instruction requires attention to students' identity development--the key developmental task of adolescence. Secondary science teachers participated in an 8-week course focused on understanding adolescent identity development and methods for addressing identity. Transcripts of the teachers' online discussions of salient issues were analyzed to determine their perceptions regarding classroom identity work. Teachers identified several assets and obstacles to identity work that were organized into two broad categories: teacher knowledge, training opportunities, and administrative support, or lack of these; and, presence of inflexible curricula, standardized testing regimes, and increased teacher accountability. Implications for student growth and science teacher professional development are discussed.