Cognitive activation is considered an important feature of high-quality teaching. Particularly for mathematics and science subjects, characteristics of cognitively activating instruction have been developed and their significance empirically confirmed. This is largely still pending for the subject of German and for the primary level. In the context of this dissertation, cognitive activation was conceptualized specifically for spelling instruction, and the empirical question was addressed regarding the effects of spelling instruction with varying levels of cognitive activation potential on the spelling competence of elementary school students. A mixed-methods design was used to conduct an intervention in the second grade. At three measurement points, the orthographic performance was assessed, and students with weaker spelling skills were interviewed about their orthographic knowledge. Both the evaluations of the spelling tests and the student interviews showed that children from the highly cognitively activating spelling instruction were able to improve more significantly over the course of the study than students from the spelling instruction at a lower cognitive activation level. This work highlights the importance of cognitive activation for spelling instruction in elementary school and is aimed at educational researchers as well as (future) primary school teachers.