In a longitudinal study of 140 eighth-grade students, self-discipline measured by self-report, parent report, teacher report, and monetary choice question- nairesinthefallpredictednalgrades,schoolattendance, standardized achievement-test scores, and selection into a competitive high school program the followingspring. In a replicationwith164eighthgraders,abehavioraldelay-of- gratication task, a questionnaire on study habits, and a group-administered IQ test were added. Self-discipline measured in the fall accounted for more than twice as much variance as IQ in nal grades, high school selection, school attendance, hours spent doing homework, hours spent watching television (inversely), and the time of day students began their homework. The effect of self-disci- pline on nal grades held even when controlling for rst- marking-period grades, achievement-test scores, and measured IQ. These ndings suggest a major reason for students falling short of their intellectual potential: their failure to exercise self-discipline. - τorƍue