This article aims to present some results of research - conducted under the Project Centre of Education, funded by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes) - on the learning and the difficulties in relation to Numbering System Decimal students of 5th year of public state and municipal São Paulo. The research was based on the results of Sistema de Avaliação da Educação Básica (Saeb) the schools involved, and taking into account theoretical studies that discuss the teaching of Decimal Numbering System, analyzed the data qualitatively and quantitatively. Among the results, we emphasize that our system of writing numbers, has characteristics that are not always built by students of the early years of elementary school.
Decimal Numbering System; external evaluations; the early years of elementary school