Charlotte Mason looks to the Gospels for her understanding of the child’s place in the world. She talks about a child as a being of eternal / heavenly origin — i.e. the verse that says we are not of this world. (This, of course, is true of adults as well; human beings, made in the image of God, were made for eternally dwelling with God.)
Mason’s point seems to be that we not look down on children as less important than ourselves, or as if they are our property; they belong to God as much as we do, and taking care of them is a grave responsibility.
Mason derives three educational commands from the Gospels: don’t offend, despise, or hinder any little children. These commands can be found in Matthew 18 and 19 as well as in their parallels in the other Gospels.
The context of the first two, found in the first part of Matthew 18, is the disciples asking Jesus who will be greatest in the kingdom of heaven, and Jesus is saying that worrying about such things is not the way to get in; instead they should be humble like children.
The context of the third, near the middle of Matthew 19, is the parents bringing children to Jesus for him to bless them, and the disciples try to keep them from bothering Jesus. He says to let them come, because the kingdom “belongs to such as these.”
Mason also quoted that last verse earlier in this section, suggesting that there is more than age that distinguishes children from adults. There is something about childhood that Jesus wants his followers to understand, respect, and emulate.
She suggests we take these three commands as a starting place for developing a method of education; that their negatives tell us not only what we should avoid in dealing with children, but imply the positives we should commit to doing.
(BTW, I think that Jesus’ comments about little ones apply not just to literal children, but to children in the faith — anyone of any age who believes in him.)
See my friend’s post on the same portion! She’s the one who introduced me to Charlotte Mason.