There is a gap between the knowledge, skills, or state of mind of the learner and what he is to learn, which it seems to me any teaching activity must seek to bridge if it is to deserve that label. Teaching activities must therefore take place at a level where the pupil can take on what it is intended he should learn.
Knowledge and the Curriculum (International Library of the Philosophy of Education Volume 12) (ed. Routledge, 2010) - ISBN: 9781135170820