Achievement gaps may reflect the cognitive impairment thought to occur in evaluative settings (e.g., classrooms) where a stereotyped identity is salient (i.e., stereotype threat). This study presents an economic model of stereotype threat that reconciles prior evidence on how student effort and performance are influenced by this social‐identity phenomenon. This study also presents empirical evidence from a framed field experiment in which students at a selective college were randomly assigned to a treatment that primed their awareness of a negatively stereotyped identity (i.e., student‐athlete). This social‐identity manipulation reduced the test‐score performance of athletes relative to non‐athletes by 12%. These negative performance effects were concentrated among male student‐athletes who also responded to the social‐identity manipulation by attempting to answer more questions. (JEL I2, C9, D0)