A friend recently told of being in a situation where they were away from home and didn't have the children’s picture Bible they usually read to their young son. To the parent’s surprise, after using their “adult” Bible, the boy said that he preferred theirs to his (except that it had no pictures.)
Sometimes we “dumb-down” our teaching, thinking that we are making it age-appropriate. Remember that Jesus told us not to look down on the little ones. (Matthew 18:10) Don’t water down your teaching. Instead, teach the children solid Biblical truth in language they can understand. Teach the saved child the truths he needs to know to win against temptation and become more Christ-like and the unsaved child the simple Gospel message.
Don’t be afraid to systematically teach your club or class theology. Children have a natural curiosity about God. Take advantage of it to teach them the truth before the world start influencing them for the lie.