Understanding relations between variables : Revisiting a ‘node’ in the development of algebraic thinking

To what extent are students, beginning at upper secondary level, able to explain the algebraic statement y = x + 5, and which representational forms do they use? Results from parts of a larger longitudinal study in Sweden are presented and compared to two other, similar studies involving students from different educational levels. This article also discusses possible strategies to improve mathematics instruction, for enabling students to acquire a higher quality of algebraic thinking, including an earlier introduction of algebra in primary school and the use of technology for multiple representations