Question

Why is early childhood a crucial time for addressing physical aggression? when aggression is still high at the end of early childhood, ____?

Answer 1

I believe the answer is: it is a strong predictor of later aggression in adolescence and adulthood

Children who display constant physical aggression toward others generally experience some sort of problem in their home (they are either being ignored by their parents or they witness their parents do it and imitate them).
If this left unhandled, the aggression would become a habit as they grow up and make it much harder to be changed.