The three agents of education
The three agents of education are the prepared environment, which will protect, nourish, and stimulate, where the child will find the freedom to construct in a space with no obstacles for natural development, protecting the child's work and distraction from the work, nourishing by providing raw materials for the stimulus of activity. The second agent is the set of proper tools, keeping his needs and capacities in mind, the best of human culture, in a form accessible to the child at this point in development. The third agent is the adult prepared spiritually and scientifically, in ways needed to approach the child from the perspective of being an assistant to life and development from a point of service. The adult who is prepared for this work by understanding the child from a perspective of psychology and understanding the technique of preparing the environment and the means of development for the child. We know that of these three agents, the only living element is the adult.
Principle of subsidiarity in the classroom
Essential aspects of the preparation of the adult: Spiritual and scientific
Responsibilities and characteristics of the adult in the child’ environment
The guide’s role changing with emergent concentration
Dr. Montessori said that the teacher has to have an active imagination. That is because the child displays many disorganized behaviors. The Montessori teacher must have faith in the child who will reveal herself through work. Work is the only solution to bring about the change in child. It is not as a magical environment, as if just put in the right environment, as if the child will immediately emerge with concentration. It takes time, but the child would not have developed these same faculties, over time, without the guide having the imagination to see what will emerge with time and effort. It is a question of a whole revolution, discovering all we are and can be, because we discover unknown factors within ourselves, and should accordingly conceive of our mission as educators.
Albert Joosten on the practice of discerning help versus hindrance
"This is not merely a question of learning something. It is a question of achieving a revolution within ourselves and of our whole outlook, of our whole attitude, and of everything we are, knowingly or unknowingly. The discover and exploration of all we are, without having been aware of it, is one of the most exhilarating and fascinating experiences because we discover unknown factors within ourselves. To try and set right the manner in which we conceive our mission, and accordingly, should fashion and shape our attitude and being, that is spiritual preparation." 
How does this look in practice? How do we know when to step away? How do we develop the capacity to recognize concentration? Fundamentally, in looking at the child, the lens is the developing child. To go beyond the behavior that needs correction, we look at the child's needs. The actions are serving the inner child, not responding to the outer behavior. This is going to be a big help in our daily practice with children. If we look at the child's activity, we question whether the activity was spontaneously chosen by the adult or by the child. Does the chosen activity serve their development? Even in established classrooms, the work that is happening may be meaningless. It is for us to question whether it supports the inner development of the child. We look at the child and decide whether it serves the child or not. The same is true if the child is imposed on the child; many times, when the adult complains that the child is not completing their work, we question why it is the teacher observes what it is the child should be doing. The imposition of activity, consciously or directly, it is based on the expectations that the adult has imposed, and the child will often complete those imposed activities, but the child will take little from it.
We should not set the expectation of what they can do when, because it hinders their ability to develop their own will and concentration. The teacher must be able to recognize the difference between positive activity and activity that does not serve development. Mr. Joosten says to intervene in the instance of misuse. If there is faulty handling of the material, you always step in. There is no way the child will ever get to the point of success without clear pointers, for example of where the lip of the pitcher should rest, or that the color tablets are not building blocks. Observing the child's activity will show whether the child had the fundamentals which will lead toward success. In most cases of observing errors, no correction is needed.