In this article, Andrew Martin, deputy head teacher at Greenside School in Stevenage, provides an outline of the development of the P scales as an assessment tool for pupils working below Level 1 of the National Curriculum. He recounts the difficulties his school found in using P scales to track pupil progress from year to year and describes and evaluates a computer package which he devised in order to fulfil this function. He goes on to discuss current issues in the use of P scales, many of which were highlighted through use of the computer package. These issues include inconsistency in the use of the P scales; variations in pupil profiles; difficulties over making "best fit" judgements; the need for moderation; and relationships with other curriculum and assessment systems in the school years and in the Foundation Stage. Andrew Martin closes his article with a call for consistency in approaches to assessment, particularly in view of the fact that P scale assessments are to be collected as part of statutory end of key stage data collection arrangements in future.