I am a great fan of Maria Montessori and her ideas about education. This page are some thoughts and links.
First we have the core pedagogy. Then we have the actual learning environment, tools, tasks, etc. Third, we have montessori training of teachers. Fourth, we have the actual 6-12 grades (which Montessori herself did not produce). Finally what would this look like in terms of higher education, both academic and professional. And Ultimately what does this look like in terms of ongoing professional development.
Note that Montessori has the same problem as TEFL where there are many online courses that have a wide variety of prices, and obviously some of them are simply inadequate, and others are rapaciously priced and overkill.