We investigate whether individuals who are made aware of their stereotypes change their behavior, studying teacher bias in Italian schools. Teachers give lower grades to immigrant students compared to natives with the same performance in standardized tests. Differences in grading are bigger for teachers with stronger stereotypes, elicited through an Implicit Associa-tion Test (IAT). We reveal teachers their own IAT score, randomizing the timing of disclosure. Teachers informed before grading increase grades assigned to immigrants. This result is driven by teachers who do not report explicit views against immigrants and who receive a more precise signal of their implicit bias. Alberto Alesina, Michela Carlana, Eliana La Ferrara, Paolo Pinotti Post-event survey: https://docs.google.com/forms/d/13auzru65OkSJAa2Bfir9w9nXe9HF32iGrESM-fcTsd4/edit#response=ACYDBNgZjFr_3ZMgjjPJs3ONVktsEH4HdzOG3vqvy8xyYjAXD9Y5Cs0GMOXur4cmr8NftOs