The present paper contributes to individual difference research in the field of working memory (WM) and reasoning and their contribution to the prediction of real-life criteria. Therefore, a broad WM test battery, a well-established measure of reasoning, and school grades were applied. It is argued that abilities as assessed with the WM component coordination are relevant for good performances at school, especially for science courses. The verbal task of the WM component storage in the context of processing was assumed to be relevant for the prediction of performance in language courses. As expected, reasoning turned out to be the best predictor of school grades. However, it was also confirmed that variance shared by coordination and reasoning can explain school performance, especially as concerns science courses. The verbal storage in the context of processing task significantly accounted for variance in language courses above and beyond reasoning. Thus, the present study provided further insights into the differential validity of different WM components.