This article takes Anderson's (1999) "code of the street" as the context for studying science learning in an inner city American public school. It is proposed that a socio-cultural model of mind can help to explain how students in an urban chemistry class negotiate contradictory cultural codes. This analysis includes a consideration of (a) interaction styles, (b) the meaning of chemistry talk, (c) the dynamics of the code of the classroom, and (d) short-term learning and long-term consequences. An analysis of microinteractional synchrony in classroom video footage is compared with ethnographic observations. It is concluded that fostering integrative identities that blend cultural codes can help to promote a new code of the classroom that values science learning. This study suggests that students sometimes use the code of the street to enhance science achievement. Exploring this phenomenon yields new information about the process of code blending and the dynamics of classroom culture. (Contains 13 footnotes.)