This study analyzed aspects of a knowledge base for teaching and ways that teachers understood and described the required student knowledge base, highlighting the construction of a knowledge base for elementary teaching. Participants were elementary teachers and staff from one Brazilian elementary school. Teachers wrote reports on what they believed was the knowledge base that students must possess at the end of the school year in order to perform efficiently in the next grade. Teachers also collaborated to prepare written reports about a shared knowledge base for each grade. Using data from interviews, observations, individual reports, group reports, official documents, and teachers' reflective diaries, researchers examined: knowledge and interpretation of national curriculum guidelines; construction of the school knowledge base; personal and professional stories; and shared professional lives. Teachers' responses were very diverse. The most frequently mentioned knowledge generally did not discriminate between the grades. Teachers attributed the most importance to content and ability related to mathematics and Portuguese. The specific content knowledge of different subjects appeared to be the nucleus of the specification of the knowledge base. Teachers considered the construction of pedagogical content knowledge the most important element necessary for learning to teach. (Contains 40 references.) (SM)