The analysis showed males with higher levels of aggression at first grade, but there were increasing and significant effects at sixth grade. (crimesolutions.gov)
These conditions can interfere with children's abilities to control their own behavior, resulting in higher levels of aggression in early and middle childhood. (sciencedaily.com)
When the children were 2 years old, those who had entered at earlier ages displayed modestly higher levels of aggression than peers who entered later. (sciencedaily.com)