What theories are the Montessori, Reggio Emilia, and Constructivist schools based on?

I am doing a research paper for Montessori, Reggio Emilia, and constructivist schools and need as much information as I can get! Other questions for each that I need are: Philosophy of the program, how the theory and philosophy are manifested in the classroom, the role the teacher plays, the role the child plays, strengths and weaknesses of each. Please help!