When a student repeats a grade, it can spell trouble for the student’s classmates, according to a new study of nearly 80,000 middle-schoolers. Higher numbers of repeaters were linked with higher suspension rates in the school as a whole, and more discipline problems such as substance abuse, fighting and classroom disruption. The study showed that when there were more older and retained students present, discipline problems increased for all subgroups in the study, including black and white students and boys and girls. Two groups saw a particularly large jump in discipline problems: white students and girls of all races.