Teachers' specialized knowledge through problem posing in pre-school education

Problem posing, as a genuinely mathematical activity, provides an inexhaustible source of alternatives in a classroom. Many authors, as well as institutions such as the National Council of Teachers of Mathematics, highlight the importance of this mathematical practice. With this case study, we intend to demonstrate the characteristics of the type of knowledge used by a teacher when implementing this type of session in 4-year-olds, with an emphasis on the knowledge used for planning and putting the session into practice. We used fragments of the session's recording, as well as a subsequent interview with the informant, in order to corroborate the information identified during the data analysis. The specific mathematical nature of this activity leads us to use the MTSK model (Mathematics Teachers' Specialized Knowledge) as a reference to analyze the specialized knowledge that a pre-school teacher uses during a classroom practice. This practice is comprised of two tasks, both created and designed by the informant teacher. Results show aspects of knowledge related to MK (Mathematical Knowledge), but, above all, PCK (Pedagogical Content Knowledge) predominance, evidencing the importance of this type of knowledge in early childhood education to implement a problem posing session.