The field of education draws on a number of other fields of knowledge as a basis for its practice. The amount of cumulative knowledge in some of them has increased enormously in the last 50 years. This has not happened in educational psychology. Some theoretical positions have been replaced by others, but often with little evidential basis for the change. A more systematic and rigorous evidence based approach is needed to maintain the credibility of educational practice. Models such as one recently developed in health practice may provide a suitable basis for educational practice.