The Core Knowledge approach maintains that a grade-by-grade core of common learning is necessary to ensure a sound and fair elementary education. The movement was started by Professor E. D. Hirsch Jr., author of Cultural Literacy and The Schools We Need, and is based on research in cognitive psychology, as well as a review of some the world's fairest and most effective school systems. Advocates of the Core Knowledge curriculum say that early schooling should provide a solid, specific, shared curriculum to help children establish strong foundations of knowledge.