Children often infer that descriptive group norms (i.e., how a group is) are prescriptive (i.e., how group members "should be"), and this descriptive-to-prescriptive tendency, which biases children against non-conformity, declines with age. We tested whether this age-related decline diverged across different types of processing. Children (ages 4 to 13) were randomly assigned to one of two conditions in which they evaluated conforming and non-conforming individuals from novel and third-person groups. In one condition, children made fast judgments, and in the other, judgments were slow. Replicating past work, children were biased toward non-conformity, and this bias declined with age, through the rate of this decline was strongest among children who made fast judgments, suggesting that encouraging children to think slowly does not necessarily undermine their descriptive-to-prescriptive tendency.