Children are taught especially by images suited to their natures, images that are unbelievably lovely and full of wisdom from within. In this way, there is gradually instilled into them an intelligence that derives its essence from goodness. I may cite at this point two examples I have been allowed to see that will serve to suggest the nature of the rest.
At first, the Lord was pictured rising from the tomb, and along with this, the uniting of his human nature with his divine nature. This was done in such a wise manner as to surpass all human wisdom, but at the same time with a childlike innocence. The idea of a tomb was presented, but with the Lord present only so remotely that one could hardly tell that it was the Lord, as though he were far off. This was because there is a sense of death in the notion of a tomb, which they were removing by this means. Then something ethereal, something that looked faint and watery was carefully let into the tomb, referring to the spiritual life represented by baptism, again from a proper distance.
Then I saw a representation of the Lord coming down to the captives and rising with the captives into heaven, presented with incomparable care and reverence. The childlike aspect of this was that little cords were let down, almost invisible, as soft and delicate as possible, which supported the Lord in his ascent. Throughout it all, there was a holy fear lest anything in the images should touch on a matter in which there was not something spiritual and heavenly.
There were other representations that engaged the children as well—for example, plays suited to the minds of children—through which they were led into awareness of truth and affections for what is good.
I was also shown the nature of their delicate understanding. When I was saying the Lord’s Prayer and they were flowing into my concepts from their own comprehension, I noticed that their inflow was so delicate and gentle that it was almost nothing but a feeling. At the same time, I noted that their understanding had been opened to the Lord, for it was as though what was coming from them was flowing through them. In fact, the Lord flows into children’s concepts, primarily from the deepest ones. Nothing has closed these off, as happens with adults—no principles of falsity closing them off from true understanding, no life of evil closing them off from accepting what is good and thus from being wise.
We may gather from all this that children do not become angels immediately after their death but are gradually led [into heaven] through awareness of what is good and true, all according to the design of heaven. This is because the least details of their nature are known to the Lord, so they are led, in cooperation with every least impulse of their inclinations, toward the acceptance of truths that arise from good and the good that is done from truth.
from Heaven and Hell, Sections 335, 336