This position paper has been produced in order to inform some of the current debates on National Curriculum Assessment in England. The Education and Skills Committee of the House of Commons has announced an inquiry into Testing and Assessment. In part this will examine testing and assessment in primary and secondary education as a key issue. Currently, pupils in England take Key Stage tests at 7 years-old, 11 years-old and 14 years-old in English, mathematics and science. This system has developed and evolved since its introduction in 1991. In January 2007 the Government announced that it would pilot several measures at Key Stages 2 and 3, including allowing pupils to sit national Curriculum assessments as soon as they are ready instead of waiting until the end of the Key Stage. This paper describes the background to these debates, concentrating on the purposes of assessment, and the desirable characteristics which flow from these purposes. This leads to a statement of the National Foundation for Educational Research's (NFER) stance in relation to assessment. Finally, a commentary is given on two specific proposals for change currently under discussion: a national monitoring system based on a sampling approach; and the "Progress Tests" proposed in the DfES discussion paper "Making Good Progress." NFER's stance is that there must be a clear statement of the intended purposes of the assessment system and that its processes and instruments should have an appropriate level of validity and reliability to provide sound evidence for those purposes.