I had an acquaintance who took upon herself to run a Montessori kindergarten in our neighborhood. She always served children a freshly baked home bread, and was always mail-ordering something very natural and expensive for her kindergarten, which eventually closed down for financial reasons. I was already vaguely familiar with the system because the mother of one of my best college friends was a regional coordinator of the Montessori kindergartens. From time to time I would hear stories about how her mother educated her and, what surprised me the most, reacted to her mis-behavior. So I knew Montessori was something good and special--and rather expensive.

So what is it? The founder of the Montessori education system was Maria Montessori (1870 –1952), who was part of the cognitive-development movement. She began to develop her educational philosophy and methods in 1897 and opened her first classroom In 1907, the Casa dei Bambini (Children's House) in Rome. Montessori based her work on her observations of children and experimentation with the environment, materials, and lessons available to them. She frequently referred to her work as "scientific pedagogy".

Montessori talked about "planes of development" or as we now call it, the stages of cognitive development and believed that it's impossible to accelerate a child's development beyond their ability at certain stage, recognized the need for repetitive behavior (motor and mental) for cognitive development, as well as the importance the environment plays in stimulating children’s mental growth and health. In fact, her views often foreshadowed those of constructivist theorists: “The known establishes itself in the child as a complex system of ideas . . . actively constructed by the child himself during a series of psychical processes representing an internal formation, psychical growth. (Montessori, 1965, p. 162-3).

Today, a range of practices exist under the name "Montessori", and according to the Association Montessori Internationale (AMI) and the American Montessori Society (AMS) these elements are essential:

• Mixed age classrooms; 
• Student choice of activity from within a prescribed range of options.
• Uninterrupted blocks of work time, ideally three hours.
• A constructivist or "discovery" model, where students learn concepts from working with materials, rather than by direct instruction.
• Specialized educational materials developed by Montessori and her collaborators often made out of natural, aesthetic materials such as wood, rather than plastic.
• A thoughtfully prepared environment where materials are organized by subject area, within reach of the child, and are appropriate in size.
• Freedom of movement within the classroom.
• A trained teacher who follows the child and is highly experienced in observing the individual child's characteristics, tendencies, innate talents and abilities.

The video below presents the Montessori middle schools and the principles they are based on. I specifically chose this over any elementary Montessori school video to show how these principles work for older 21st century children.

Constructivism, as noted in this week's updates by many, on the following basic principles: 

• Lessons have to be relevant to the lerner and “sparks their interest”;
• Lessons center on the “less is more” concept, where students construct their own meaning in a way that they best understand.
• Adults see and value their student’s point of view.  
• Curriculum tasks are adapted to address students’ assumptions and hypothesis which students are cognitively able to understand.
• Teachers mediate and assess rather than teach and test. 

As we can see that despite the differences (like different cognitive development stages, the role of a teacher/ facilitator, and the role of group/peer work among others) there are clear parallels between the Montessori system and constructivism, and it's fascinating that the former came into being more than half a century earlier.

Of course, the question is always the scalability of the method, and in this sense, it seems to be more challenging to implement the Montessori principles (remember my acquaintance shipping the wooden toys to her kindergarten) than to follow the constructivist approach in any classroom. Still, it's nice to note that authentic, learner - centered learning was, is, and probably will be based on essentially the same principles.

Sources: http://montessoritraining.blogspot.lt/2007/07/why-montessori-part-i.html

https://en.wikipedia.org/wiki/Montessori_education