The teaching of second languages in school classrooms is often conducted through the use of 'direct' and 'immersion' methods, while grammar is reserved for the first language. However, pupils spontaneously raise important questions for general and theoretical linguistics which could be better addressed through an interlinguistic comparison of first and second language grammars in the pupils' repertoires. This paper explains the method used in a pilot experiment in fieldwork. The experiment was conducted in * The author thanks all the staff of the Montessori school in via Milazzo, Milan, Italy for the collaboration in the fieldwork, and in particular: the teachers Chiara Bonizzoli and Patrizia Pradella, and the head Costanza Buttafava, for the possibility to inspect Maria Montessori's manuscript Psicogrammatica, which we all hope that will be published soon. A special acknowledgement goes to Grazia Honegger Fresco, who offered a wonderful tea time to the author, where language teaching and many other stuffs were discussed. 114 Learning Linguistics by Doing: The Secret Virtues of a Languaget he fourth class of a Montessori primary school, where pupils constructed from scratch a posteriori language to be used for secret communication among themselves-but not to be used with the rest of the school. During the process of the construction of this language, all aspects were discussed in the class: phonetics and writing systems, morphology and syntax, semantics and pragmatics. The main educational result was the increase in pupils' metalinguistic awareness, as well as the confidence that they gained in their own language proficiency.