Several studies have shown that children with a migrational background and a non-academic background lack sufficient language competencies in grade four and later on in their school career. In order to improve the situation for those children, a systematic language approach is tested and evaluated in the case study described in this contribution. The goal of the study is to give a deeper insight into the conditions under which the acquisition of written language is possible for everyone. The central aspect of the approach presented is that every lesson is considered to be a language lesson. New, theory-based and linguistically valid learning material is applied to the sample of first and second graders. The concept is based on didactic and psychometric fundamental research and on results of qualitative pre-studies. The children are compared to a control group with standardized tests. Because of the close relationship between children, teacher and researcher, the approach can be constantly adjusted to the children’s needs. Therefore, this approach is not only theory-based but also a child-oriented. The findings of the study are supposed to facilitate the further development of learning material and additional teacher training.