Lead
The impulse to introduce addition before kindergarten, or to have a child practice writing numerals, is understandable. "Earlier means more prepared" is an intuitive heuristic. But developmental research returns a consistent finding: there is a set of precursor skills that need to be in place before formal arithmetic makes conceptual sense, and drilling on calculation before those foundations are solid tends not to translate into lasting mathematical ability.
How does numerical understanding actually develop? What does the longitudinal evidence say about what genuinely prepares children for school mathematics? This article draws on Sarama and Clements's learning trajectories framework and related longitudinal research to map the development from infancy through the preschool years.