“…Some of the specific interventions developed in the field of teacher education based on the DMKC model have used the didactic competence tool, its components and indicators (Godino, 2013) to organise teachers' systematic reflection on their own practice or that of others and to develop the competence to evaluate planned or implemented instructional processes (Breda et al, 2018;Font et al, 2018;Giacomone et al, 2018;Hummes et al, 2019;Morales-López and Araya-Román, 2020;Pino-Fan et al, 2013). Some of these studies have dealt specifically with the mathematical content of proportionality (Burgos et al, 2018;Castillo et al, 2021;Esqué & Breda, 2021). Despite the longitudinal and cross-cutting importance of this content in the primary and secondary curricula, as well as being the bridge to advanced mathematical thinking, proportionality is often not adequately addressed in school mathematics textbooks at both stages (Ahl, 2016;Burgos, Castillo et al, 2020;Shield & Dole, 2013).…”