Current approaches to developing the National Curriculum involve setting attainment targets which are to inform teaching and which are to be the basis of National Assessment tests. It has not been easy to arrive at these targets in mathematics and science. It is claimed that it will be considerably harder in other curriculum areas, the humanities for example, where there has been little research into the development of children's understanding. A report of an investigation of 6-14 year old children's developing understanding of people in the past illustrates the nature of the problem facing curriculum makers in these domains.