The purpose of the current empirical research, which departs from a socio-psychological perspective in terms of the concept of diagnostic teaching, is to explore and analyze mathematics teachers’ reflections about students’ learning of algebra.

The theoretical approach proposed by Bernstein and Miller, and the concept of inverse operations in algebra was applied. In this theoretical context, the purpose of developing a diagnostic framework is to include a conceptual triangulation of three domains: (1) conscious inclusion in the teaching environment of a component that addresses students’ different levels of prior knowledge and mathematical experience; (2) teacher-student content-oriented conceptual communication; and (3) a gradual sequencing of teaching content.

The methodological approach is a mathematical intervention, based on the main principles of the diagnostic framework conceptualization that is rooted in the Swedish PUMP project. The methodological tools are based on qualitative research and data collection from secondary school teachers’ group discussions, teachers’ analysis of students’ diagnostic tests, and written reflections. The participants comprise three teachers and 94 students. The crucial content of the study is a conceptual transition from whole and rational numbers to algebraic equations and problem-solving.

The findings of the study illustrate that teachers are aware of the importance of diagnostic teaching and the implementation of diagnostics in the teaching of algebra, practical awareness of students’ knowledge of algebra, and what should be taught. The results of the study show teachers’ practices and the challenges they face with handling mathematical content and content-oriented communication. The findings clearly indicate that diagnostic teaching that addresses students’ mathematical needs and teachers’ reflective teaching practice directed at student learning have not been fully developed in practice.