While there are official Montessori institutions in different countries providing teacher training and accreditation, this is not necessary for schools to use the term in their advertising.
Ironically, however, many schools today bear Maria Montessori's name while only loosely adhering to her methods. This is because the word is not trademarked. While there are official Montessori institutions in different countries providing teacher training and accreditation, this is not necessary for schools to use the term in their advertising.