Theory of didactical suitability: An enlarged view of the quality of mathematics instruction

Characterizing and measuring the quality of instruction is a matter of growing interest in mathematics education. Based on the notion of didactic suitability and the theoretical assumptions of the onto-semiotic approach, we develop an instrument to systematically analyze the different facets involved in a mathematics instruction process. We also explore the concordances and complementarities with instruments for measuring the quality of instruction. Thus, quantitative quality measurement efforts are complemented by another qualitative approach, focusing on the initiative and responsibility of teachers when they have to make decisions about their teaching practices. This reflective activity must be supported by specific instruments that reveal the complexity of the processes and the difficulty of achieving a balance between sometimes conflicting didactic principles.