Key ideas as guiding principles to support algebraic thinking in German primary schools

German mathematics teaching-units in primary school lack explicit algebra learning environments; however, the topics which are taught address algebraic thinking if seen from a new perspective. Teachers and children are mostly unaware of the algebraic potentials of tasks –especially in the scope of the content area patterns and structures. The project presented here submits a suggestion of algebraic key ideas as guiding principles to rethink ‘arithmetical’ topics and to design learning environments on algebraic thinking. Additionally, effects of implementing and evaluating such tasks are illustrated by one example.