Many significant changes in perspective have to take place before efforts to learn the content and capabilities of children's minds can hold much sway in educational testing. The language of testing, especially of high stakes testing, remains firmly in the realm of "behaviors", "performance" and "competency" defined in terms of behaviors, test items, or observations. What is on children's minds is not taken into account as integral to the test design and interpretation process. The point of this article is to argue that behaviorist-based validation models are ill-founded, and to recommend basing tests on cognitive models that theorize the content and capabilities of children's minds in terms of such features as meta-cognition, reasoning strategies, and principles of sound thinking. This approach is the one most likely to yield the construct validity for tests long endorsed by many testing theorists. The implications of adopting a cognitive basis for testing that might be upsetting to many current practices are explored.