The issue of correct practice (i.e., according to Henri Louis Go, practice that reflects the spirit and letter of a pedagogy), concerns every pedagogue, and Maria Montessori certainly took correct practice very seriously from the outset. Indeed, her emphasis on this crucial issue explains some of the strategic choices she made, as well as the ways she promoted her method abroad, and the relationships she maintained with her contemporaries (analyzed here via the early years of the journal Pour l’Ère nouvelle). These all led to accusations of dogmatism or pedagogical orthodoxy that continue to be leveled at the Montessori network today. This article sets out to explore the controversy surrounding the issue of correct practice in the field of pedagogy, taking Montessori as its example. Focusing on the 1920s, it considers the questions raised by attempts to protect a life’s work within a heterogeneous array of philosophical and political practices and positions. It also explores the reticence that some of Montessori’s contemporaries (particularly Decroly and Ferrière) showednot toward her pedagogy per se, but toward the way she conceived of and applied this pedagogy.