**3. Research project**

The research findings presented in the theoretical part of the article show that there is already a lot of research on the conversion of teaching to distance learning and its effects on children and adolescents. It shows that some children have come through the pandemic well, while others have major deficits [26–28]. In mathematics, it is shown that students benefit from activity-based, material-supported instruction and especially from activity-based engagement with Montessori materials to achieve high levels of competence in mathematics [4, 12, 13, 29, 30]. When teachers have completed Montessori training, they implement elements of the concept in their teaching and use Montessori didactic materials, especially in mathematics [4, 31, 32].

During distance learning, the teaching methods had to be changed and adapted; the lessons took place at home and the students could not work with the materials in a proven way. Research in the field of mathematics is scarce for the German-speaking countries. The question arises whether students who were already able to build up mathematical competencies during face-to-face teaching through active engagement with Montessori materials could benefit from this during distance learning [11].

The research desideratum gives rise to the following research question for the study presented here: What features of action-based, materials-supported mathematics instruction do Montessori teachers judge to be conducive to developing mathematical competencies during distance learning in times of the COVID-19 pandemic? [11].

The purpose of this study is to find out how adaptable Montessori's educational concept is to the needs of children in the 21st century, especially in the area of mathematics, and whether recommendations for school and classroom development can be derived from it.

Within the framework of the study, a second question concerning the self-organization of learning processes was also addressed. However, this cannot be addressed in this article.
