Theoretical Foundations for Constructivist Teaching

Constructivism is a theory of knowledge that explain how people learn.  People learn when they construct their own knowledge and understanding of the world.  They generate knowledge from the interaction of their experiences and their ideas. Learners are actively engaged with the information.
Constructivist theory today is broad- based and incorporates  cognitive constructivism of Jean Piaget and social constructivism  of Lev Vygotsky.
Piaget's theory of cognitive development is based on assumption that people try to make sense of the world and actively create knowledge through direct experiences with objects, people and ideas.  Maturation, activity and social experiences affect changes in our thinking. People tend to  organize their thinking processes into psychological structures. Piaget calls these psychological structures schemes. Schemes are organized systems of actions or thought that allows us to mentally represent or think about object and events in our world.
In addition to organizing their mental images, people  tend to adapt to their environment.  They do so by either assimilation or accommodation.   Assimilation happens when people trying to understand something new, fit this new information into what they already know ( their existing schemes).
If new information cannot fit existing schemes, we adjust our thinking to fit the new information.
The actual changes in thinking take place through equilibration, act of searching for balance between  cognitive schemes and information from the environment. 
Piaget believed that  all people pass through the same four stages of cognitive development in the same order. As the author of the text emphasizes the three stages of cognitive development that are important for teachers are: preoperational stage ( 2-7 years old), concrete operations stage ( 7-12) and the formal operations stage ( 12 years old and beyond).
Knowing the characteristics of these stages helps teacher understand how children think and learn and it guides to teacher how to plan instruction for different ages of children. So if we know that children 4-7 years of age, in the later part of preoprational stage, use intuitive thinking we  know that they use typially  their sense impressions instead of  logic in forming judgements.  In concrete operational stage children are logical thinkers but they need firsthand experience  with the materials to understand the ideas we are teaching them.  In the later stage of formal operations children can think abstractly.  They don't need concrete objects, they use symbols related to abstract concepts.
Piaget believed that mind models the external world.  Humans make sense of their world by means of their mental structures.  Piaget sees development as leading learning.  Vygotsky saw learning as leading development.  He places more emphasis on the culture and society in affecting and shaping cognitive development.  While Piaget emphasized self-initiated discovery, Vygotsky believed that much important learning occurs through social interaction  with more knowledgeable members of society. 
Knowing how children learn through constructivist theory, I would have to bear in mind that my role as educator would be to prompt and facilitate discussion by modeling, coaching and scaffolding.
The activities in the classroom should be interactive and student- centered.  I would need to keep students involved in the lesson  through the use of challenging and open-ended activities that foster discussion.  Students would primarily work in groups as they can exchange ideas.