Evidence of Professional Knowledge of a 4th-grade Mathematics Teacher from the Perspective of a Research Project Involving Lesson Study

Context: Lesson Study has been used in several countries in the West and East with adaptations to the possibilities of local education systems and cultures. Objectives: The article discusses and analyses the knowledge to teach mathematics evidenced by a teacher who taught in the fourth grade of elementary school in the municipal education network of São Paulo and who participated in a research project using the lesson study training methodology. Design: The study is situated in qualitative research, with an interpretive nature. Setting and participants: It involves teachers from the interdisciplinary cycle who teach mathematics in the municipal education network of São Paulo, especially a teacher who worked in the fourth grade of elementary school. The training with the teachers was carried out fortnightly at the Cruzeiro do Sul University. Data collection and analysis: The analysis was based on empirical material consisting of observational protocols, training audios, photographs of students’ curriculum materials, and transcripts of video recordings during class observation. Results: The research results show that the teacher’s gaps in her knowledge to teach mathematics were shown in the class observation stage, even without appearing in the planning, and that the discussion in the reflection stage allowed the teacher to progress in her practice. Conclusions: With the training actions, the teacher’s didactic and curricular knowledge was produced from discussions with the group, based on theoretical contributions that dealt with the mathematics teaching and learning process