Charlotte Mason quotes William Wordsworth's poem "Intimations of Immortality from Recollections of Early Childhood " on p. 11 of Volume I, Home Education. The context of this quote is that children are not simply "a tablet to be written on, a twig to be bent or wax to be molded. No, they are so much more than that. As we will see from the poem below, they belong to a higher estate than ours.  

Our birth is but a sleep and a forgetting:
The soul that rises with us, our life’s star,
Hath had elsewhere in its setting,
And cometh from afar;
Not in entire forgetfulness,
And not in utter nakedness,
But in trailing clouds of glory do we come
From God, who is our home:
Heaven lies about us in our infancy!

* * * * * * * *

Thou, whose exterior semblance doth belie
Thy soul’s immensity;
Thou best philosopher, who yet dost keep
Thy heritage; thou eye among the blind,
That, deaf and silent, read’st the eternal deep,
Haunted for ever by the eternal mind
Mighty Prophet! Seer blest!
On whom those truths do rest,
Which we are toiling all our lives to find
Thou, over whom they immortality
Broods like a day, a master o’er a slave,
A presence which is not be put by;
Thou little child, yet glorious in the might
Of heaven born freedom, on they being’s height––
— William Wadsworth

Note: The above quote is an excerpt from the poem in its entirety. You can find Wordsworth's full ode here.