The life of every day, of every moment, is the best school of all, varied, complex, full of unexpected experiences, problems to be solved, clear and striking examples and obvious consequences. It is so easy to arouse healthy curiosity in children, if you answer with intelligence and clarity the numerous questions they ask. An interesting reply to one readily brings others in its train and so the attentive child learns without effort much more than he usually does in the classroom. By a choice made with care and insight, you should also teach him to enjoy good reading-matter which is both instructive and attractive. Do not be afraid of anything that awakens and pleases his imagination; imagination develops the creative mental faculty and through it study becomes living and the mind develops in joy.
In order to increase the suppleness and comprehensiveness of his mind, one should see not only that he studies many varied topics, but above all that a single subject is approached in various ways, so that the child understands in a practical manner that there are many ways of facing the same intellectual problem, of considering it and solving it. This will remove all rigidity from his brain and at the same time it will make his thinking richer and more supple and prepare it for a more complex and comprehensive synthesis. In this way also the child will be imbued with the sense of the extreme relativity of mental learning and, little by little, an aspiration for a truer source of knowledge will awaken in him.
Ref : On Education