The 1988 Education Reform Act ushered in a new era in education within Britain. Before this Act, the government had had no recent and direct control over the school curriculum. Now there is a prescribed curriculum in all main subjects, with associated national testing at four stages within the years of compulsory schooling. This article describes the evolution of this policy. The story starts with a sketch of the background to the 1988 legislation. There is then a first account of the formulation of assessment policy, given here because the formulation of the science standards can only be understood in the context of this policy. There then follows an account, with examples, of the three versions of the national curriculum for science which have appeared over the past seven years. In order to understand these more fully, the article then returns to assessment in order to trace the evolution of the policy and practice in this area over the same period of time. The closing section presents some reflections on the issues illustrated by this strange story.The account applies only to England and Wales. Although the word 'national' is used throughout, the legislative arrangements for Scotland and for Northern Ireland are different and are not discussed here.