Clinical cognitive ability assessment--and its corollary, score interpretation--are in a state of disarray. Many current instruments are designed to provide a bevy of scores to appeal to a variety of school psychologists. These scores are not all grounded in the attribute's theory or developed from sound measurement or psychometric theory. Thus, for a given instrument, there can be substantial variation between school psychologists when interpreting scores from the same instrument. This is contrary to the very purpose of psychological assessment. As a contrast, we provide a sketch of theoretically driven test development and score interpretation. In addition, we provide examples of how this could be implemented using two theories of intelligence (Spearman's two-factor and Cattell and Horn's Gf-Gc) and measurement theory about the nature of psychological test scores. While different from what is often implemented by school psychologists, it is consistent with the guiding principles of evidence-based psychological assessment.