It always fills me with horror to see a teacher standing in his class with a book in his hand teaching out of the book, or a notebook in which he has noted down the questions he wants to ask the children and to which he keeps referring. The child does not appear to notice this with his upper consciousness, it is true; but if you are aware of these things then you will see that the children have subconscious wisdom and say to themselves: He does not himself know what I am supposed to be learning. Why should I learn what he does not know? This is always the judgment that is passed by the subconscious nature of children who are taught by their teacher out of a book.
Such are the imponderable and subtle things that are so extremely important in teaching. For as soon as the subconscious of the child notices that the teacher himself does not know something he has to teach, but has to look it up in a book first, then the child considers it unnecessary that he should learn it either.
Source: Rudolf Steiner – GA 311 – Kingdom of Childhood: Lecture 3 – Torquai, 14th August 1924