DIDUNAS addresses an issue of concern in several countries of the European Union, that is, students’ under-achievement in mathematics. Students who do not achieve a satisfactory level of competence in mathematics are not equipped with the basic skills to cope in a numerate society. Engagement with mathematical topics develops the knowledge, skills and thinking capacity required by the majority of available jobs in the modern world. Further, mathematics is not only a core topic across all curricula but also mathematics competence influences students’ performance in other science subjects. By focusing on students’ under-achievement in mathematics, DIDUNAS intends to enhance students’ learning opportunities and to reduce the percentage of students who leave school early without a qualification to get a job, which hinders the future prosperity and social cohesion of the EU as it is a major risk for unemployment and poverty. 

Student difficulties in mathematics are seen to begin from early primary education and can – due to insufficient support – cascade into severe mathematical problems during learner biographies, which can even lead to functional innumeracy of students when leaving school. Therefore, it is significant to identify and characterize learning difficulties early in schooling, for teachers to be aware of initial difficulties and unfavorable preconditions, and to foster students adequately. Yet, identifying student difficulties at an early age is a challenging task for teachers – not least because young children tend to lack the ability to report meta-cognitively about their difficulties.