Prior research suggests that students endorsing a science identity are more likely to participate in optional science experiences and choose STEM careers. Science identity is a topical identity, which refers to an identity related to a topic rather than a social or cultural group. However, studies of topical identities typically examine them in isolation. The current study identified typically occurring combinations of topical identities as identity complexes to determine whether science identity would tend to occur within STEM-only complexes or together within larger topical identity complexes. Over 1200 urban public-school students in 6th, 7th, and 9th grades from two different regions in the USA completed surveys asking about their topical identities, choice preferences, and optional science experiences. Latent class analyses revealed that students often endorse science identities in the context of other unrelated identities like athletic and artistic identities. Further, the frequency (overall and relative to each other) of the two high-science identity complexes varied substantially by gender, ethnicity, and grade. These patterns were not simple reflects of the commonly observed overall rates of science identity by demographics. Further, students in topical complexes with high science identity still had high participation in optional science experiences despite having many topical identities that could compete for time.