The current study investigated whether teaching was associated with improved legal understanding among adolescents and adults. Participants included 927 youth and 466 young adults, who completed the MacArthur Competence Assessment Tool-Criminal Adjudication, the Massachusetts Youth Screening Instrument-Second Version, and the Wechsler Abbreviated Scale of Intelligence. Adolescents aged 13 and younger were less likely than older individuals to improve with teaching. IQ score was positively associated with improvements following teaching, and individuals from ethnic minority groups showed greater improvements following teaching than non-Hispanic Caucasians. The implications of these findings are discussed.