I have never noticed this before, but it was in front of my face the entire time. In Ephesians 6:1 Paul says, "Children, obey your parents in the Lord, for this is right." Did you catch that? This verse assumes that the children were among the rest of the congregation when the letter was being read. Not only does it assume that they were present, but that they were listening. This is astounding in our culture where most don't expect children to be able to sit down and listen for more than 5 minutes. Yet, apparently, Paul fully expected that the children would be listening to the entire letter; so, he addresses them also. He isn't talking about children, he is talking to children. (this also occurs in Colossians 3:20)
Remember, Ephesians (and neither is Colossians) is not a lightweight book and I doubt they used puppets to read it to the children. Nor did they take a break from reading the epistle, call the children down front, and do an object lesson. It is sad how far our church culture has strayed from the historic church and its expectations for children. They were expected to know by heart lengthy catechisms and, in the early church, to listen to the entirety of Paul's letters. It is time the American church raises the bar in its expectations for children and their knowledge of the Word of God.