In this article, we relate an experience in which we have used number sentences to begin to develop algebraic thinking. Working with third-graders during six sessions, we set out to explore the following questions: How do students’ conceptions of the equal sign evolve when considering and discussing varied True/False number sentences? Do students develop relational thinking while we negotiate the meaning of the equal sign? Do students retain the new interpretation of the equal sign over time? We successfully helped the students to broaden their conceptions through the different tasks but were only partially successful at initiating relational thinking. The particularities of both developments are here described
