Working memory capacity (WMC) measures for children are unsatisfying in terms of lack of operational continuity with measures for adolescents and adults. Thus, we developed and validated a multivariate WMC test battery that uses WMC paradigms that can be applied from 1st grade onwards. In Study 1, we developed child-contextualized WMC tests and investigated their psychometric properties (including gender differences) in N = 343 1st graders. In Study 2, we juxtaposed child-contextualized and decontextualized instantiations of our tasks in N = 379 5th–10th graders. Child-contextualized tests were essentially equivalent to structurally identical, decontextualized WMC tests, and the battery correlated strongly with a multivariate measure of fluid intelligence. Across studies, we found support for good psychometric properties of the tests. The battery bridges the gap between child-specific and decontextualized WMC tests, is applicable for all ability levels, can be adapted easily in terms of difficulty and length.