"Montessori" on its own does not mean too much: there are large gaps between AMI Montessori and Froebel, London School etc.

AMI only accepts trainee teachers who have already have a bachelors (as a minimum) and their pedagogy seems to be more rooted in experimental results than simply psychological theories (see e.g. Angeline Lillard's book for further details http://www.montessori-science.org/montessori_science_genius.... )