This paper presents the implementation of a new concept of first and second language assessment for pre-school children between four and six years. The concept is theoretically grounded in usage-based linguistics. It assesses language in authentic communicative settings in a game based app. The settings provide the children with incentives to engage in communication. As a result, the assessment tool does not evaluate formal aspects of language. Instead it relies on functional categories for evaluation. Norms for evaluations are derived from longitudinal corpus studies of authentic child language production. The goal of the new approach is to generate an accurate and fair assessments of the children’s communicative capacities. Pilot studies indicate that children with L2 German appear to be more advanced than shown by traditional form-based assessment methods.