Studies show that it is essential to empirically research innovative and theory-based concepts on teaching orthography. Momentarily, cost and earning in teaching orthography greatly diverge. On top of that, there is a lack in theory-based and well-researched approaches to orthography which is evidently not only closely related to reading and other language competencies, but also a decisive factor for the future working situation of the children. Therefore, the study presented in this contribution combines a didactic approach including a theoretical framework based on the linguistic fields of graphemics with educational research, using confirmatory data analysis methods based on the item-response theory. It was conducted with 600 fifth-graders in Hamburg and serves as a pilot study for the orthography test (grade 5) in the National Education Panel Study (NEPS). The study made it possible to show how children, especially the ones with lower social and migrational background, can still access the written language in secondary school. Furthermore, it could be proven that there is a functional relationship between orthography and reading competencies. Hence, it is useful to introduce the simple and yet valid and theory-based approach to teaching orthography by concentrating on the structure and its few principles for the core area of the German written language system.