The First Three Years and Aggression.

Children who witnessed domestic violence before age three were more likely to show aggression when they reached grade school, even if they were removed from their home and witnessed no domestic violence in the interim. According to Dr. Megan Holmes, the study’s lead author, “[This] gives social workers a window of opportunity between ages 3 and 5 to help the children socialize and learn what is appropriate behavior.”
Psychology and Psychiatry, March 2013