What is the Pupil Achievement Tracker?

The following information has been obtained from the Standards Site at  http://www.standards.dfes.gov.uk/performance/pat/

" The Pupil Achievement Tracker (PAT) is a powerful piece of diagnostic and analytical software. Teachers can use it to ask questions about the effectiveness of their classroom practice looking at graphical data on the progress made by their pupils; set pupil targets informed by the progress made by similar pupils nationally; and understand fully what pupils can achieve by the diagnostic analysis of test papers."