The topic of this study relates to the report to the mathematical knowledge to teach in the teachers of the primary education. It is a question of anlyzing this phenomenon and of understanding the teaching practices during the lessons of mathematics. For that, direct observations of class followed by individual interviews are carried out on a sample of nine teachers selected in three school groups of the town of Boufle in Ivory Coast. The results prove that the report with the mathematical knowledge of the teachers depends on the sector of teaching (literary or scientific) that they followed in high school. This profile also justifies their practices of teaching of mathematics. Thus, the success of the pupils in mathematics is in relation to the chance to have met during the primary cycle, effective teachers in this matter.