In The Advanced Montessori Method, Dr. Montessori wrote that, after new students — disorderly; taking things from other children; not picking up after themselves; unable to take care of themselves — get used to Montessori methods, materials and work:
The children themselves seem to have the “sensation” of their spiritual growth, a consciousness of the acquisitions they are making by thus amplifying their own personalities; they demonstrate with joyous effusion the higher process which is beginning within them. “All the children,” says Miss George, “show that pride we ourselves experience when we have really produced something novel. They skip round me and throw their arms about my neck, when they have learnt to do some simple thing, saying: “I did it all alone, you did not think I could have done that; I did it better today than yesterday.”
It is after these manifestations that a true discipline is established, the most obvious results of which are closely related to what we will call “respect for the work of others and consideration for the rights of others”. Henceforward a child no longer attempts to take away another’s work; even if he covets it, he waits patiently until the object is free; and very often a child becomes interested in watching a companion at work on some object he would like to use himself. Afterwards, when discipline has been established by these internal processes, it will happen all at once that a child will work quite independently of the others, almost as if to develop his own personality; but no “moral isolation” results from such work; on the contrary, there is a mutual respect and affection between the children, a sentiment which unites instead of separating; and hence is born that complex discipline which, moreover, contains within itself the sentiment that must accompany the order of a community. (pp. 72-73, The Advanced Montessori Method – I (formerly Spontaneous Activity in Education) by Dr. Maria Montessori, trans.s Florence Simmonds and Lily Hutchinson, Clio Press, Oxford, (c) 1991 Montessori-Pierson Estates, ISBN 1-85109-114-9.)
Update (5:10 PM): Deleted a parenthetical from the first sentence.