This Rudolf Steiner essay (from 1924) starts with standard “kids are different at different ages” stuff.
This, however, is something that people notice, and it would be considered brutal to try and keep the child's feet small enough to go on wearing the same-sized shoes! Yet this is what is being done with the soul when I furnish the child with ideas that do not grow with the person. I am constantly squeezing the soul into the ideas I give the child.
These are some of the ways in which you may begin to answer the challenge that in education you must take the whole human being into consideration -the growing, living human being, and not just an abstract idea.
It is only when you have the right conception of human life as a connected whole that you come to realize how different from one another the various ages are.
Then, a couple paragraphs later:
Well, my dear friends, suppose all you clever and well-brought-up people were suddenly condemned to remain always in a room having a temperature of 144 degrees Fahrenheit? You couldn't do it! It is even harder for the spirit of the child, which has descended from the spiritual worlds, to accustom itself to earthly conditions. The spirit, suddenly transported into a completely different world, with the new experience of having a body to carry about, acts as we see the child act.