Because hurting other people is unacceptable in the adult world and potentially harmful, do not allow children to behave this way.
Many children fight when they are angry.
They do not like something another child did and they retaliate. Or they may want something another child has and see force as the easiest way to get it. Most children try aggressive behaviors because they see other children or people on TV behave this way. If children get what they want by hitting, this behavior will become more frequent. Occasionally children become excessively aggressive because they receive lots of spankings at home or witness spouse or sibling abuse.