Within public schools, the same differential pattern is found. Using three wave of longitudinal data collected in schools, the authors evaluate several explanations for disparity. The greater rates of punishment for blacks occur as a consequence of teachers' perceptions of the student's behavior, their knowledge of students' recent academic performance, and their knowledge of student's past record of being sanctioned. Since black adolescents in the sample received poorer grades and were rated as less well behaved in the past, they were more likely to have been sanctioned and therefore to acquire a cumulative disadvantage. The punishment disparity is best understood as the result of a social construction process. (Publisher abstract modified)