I just discovered the book How Gertrude Teaches Her Children by Johann Pestalozzi, published in 1894. Here's a wonderful excerpt that, unfortunately, is still relevant over 100 years later:
"I am convinced that nature brings the children, even at this age [three], to a very definite consciousness of innumerable objects. It only needs that we should, with psychological art, unite speech with this knowledge, in order to bring it to a high degree of clearness; and so enable us to connect the foundations of many-sided arts and truths to that which nature herself teaches, and also to use what nature teaches as a means of explaining all the fundamentals of art and truth that can be connected with them. Their power and their experience both are great at this age; but our unpsychological schools are essentially only artificial stifling-machines for destroying all the results of the power and experience that nature herself brings to life in them.
"You know it, my friend. But for a moment picture to yourself the horror of this murder. We leave children, up to their fifth year, in the full enjoyment of nature; we let every impression of nature work upon them; they feel their power; they already know full well the joy of unrestrained liberty and all its charms. The free natural bent which the sensuous happy wild thing takes in his development, has in them already taken its most decided direction. And after they have enjoyed this happiness of sensuous life for five whole years, we make all nature round them vanish from before their eyes; tyrannically stop the delightful course of their unrestrained freedom, pen them up like sheep, whole flocks huddled together, in stinking rooms; pitilessly chain them for hours, days, weeks, months, years, to the contemplation of unattractive and monotonous letters (and, contrasted with their former condition), to a maddening course of life… Friend, tell me, can the sword that severs the neck, and sends the criminal from life to death, have more effect upon his body than this change, from the beautiful guidance of nature, which they have enjoyed so long, to the mean and miserable school course, has upon the souls of children?"