Abstract
The aim of this research is to provide the teacher with a useful tool for assessing problem solving processes in primary school students. Our attention is focused on formative assessment. Starting from this choice, we deepen the theme of assessment in mathematics, in particular we focus on a specific mathematical component linked with the strategic process. To this end, we describe a tool that allows us to describe the behavior of the students involved in solving a mathematical problem. This tool, called «behavior coding tool», is based on the model presented by Alan H. Schoenfeld on the study of the problem solving process. To validate the tool we select and analyse two mathematics tasks that we subsequently present to a group of primary school students. In this paper we will see how the presented «behavior coding tool» is functional to teachers who intend assessing students involved in a mathematics task and monitoring the problem solving process.