Abstract: | Three hundred and eighty-three children in grades 1–5 were individually interviewed to find out at when they construct unit iteration out of transitive reasoning as described by Piaget, Inhelder, and Szeminska (1960) . The results indicated that most children (72%) construct transitive reasoning by second grade and that most (76%) construct unit iteration out of transitive reasoning by fourth grade. The article explains why traditional instruction produces the poor results revealed by the National Assessment of Educational Progress. It also suggests a better approach to the teaching of measurement that presents problems and encourages children to modify their ways of thinking. |