We may gather from this what the upbringing of children is like in heaven—through an understanding of truth and a wisdom about what is good, they are led into an angelic life, which consists of love for the Lord and a mutual love in which there is innocence.
An example may serve to illustrate how different the upbringing of children on earth is in many instances. I was on the street of a large city and saw some boys fighting with each other. A crowd gathered and watched this with great delight, and I was told that the parents themselves urged their children into fights like these. The good spirits and angels who were seeing all this through my eyes were so repelled that I could feel them shudder, especially at the fact that the parents were encouraging this kind of behavior. They said that by doing this they would at the very earliest age stifle all the mutual love and all the innocence that little ones receive from the Lord and lead them into hatred and vindictiveness. So by their own deliberate practices they would shut their children out of heaven, where there is nothing but mutual love. Let any parents who wish well for their children beware of things like this.
We need also to describe the difference between people who die as children and people who die as adults. People who die as adults have a plane acquired from the earthly, material world, and they take it with them. This plane is their memory and its natural, physical sensitivity. This stays fixed and then goes dormant; but it still serves their thought after death as an outmost plane because their thinking flows into it. This is why the nature of this plane and the way their rational activity answers to its contents determines the nature of the individual after death.
People who have died in childhood and have been raised in heaven, though, do not have this kind of plane. They have a natural-spiritual plane because they bring with them nothing from the material world or their earthly bodies. This means that they cannot be engrossed in such crude affections and consequent thoughts. They actually derive everything from heaven.
Not only that, little children are unaware that they were born on earth, so they think they were born in heaven. This means they do not know what any birth is other than the spiritual birth that is accomplished through familiarity with what is good and true and through the intelligence and wisdom that make people truly human. Since these come from the Lord, they believe that they belong to the Lord himself, and love to have it so.
However, the state of people who have grown up on earth can become just as perfect as the state of children who have grown up in heaven if they move away from the physical and earthly loves, love for themselves and love for the world, and accept spiritual loves in their stead.
from Heaven and Hell, Sections 344, 345