These guidelines from Children’s Ministry Magazine describe how profanity affects children:
Ages 2 to 5
Preschoolers simply repeat what they hear, so try to limit media exposure. Don’t react to foul language with shock or anger; calmly explain that those words hurt people’s feelings.
Ages 6 to 9
Explain that words are “bad” when they’re used to hurt others. Also explain that misusing God’s name is disrespectful. Tell children we can use God’s name to praise him or pray to him.
Ages 10 to 12
Preteens use profanity to get a reaction from adults and to impress friends. Let them know that obscene language and gestures aren’t acceptable, and teach them discernment to censor their own language.