Rather than "casting a shadow over the credibility of national test results," as The TES asserts, the better explanation for the difference in results is that children are improving their understanding of the broad concept of language, not in the narrow skills of the PIPS test.
The tests of English are known to be a valid measure of the curriculum, reflecting the literacy strategy and what is taught in schools. As such, they provide the best measure of standards in English. The TES should recognise that fact and be celebrating the achievements of primary teachers and pupils.
National Foundation for Educational Research
(NFER develops national curriculum tests in English at key stage 2)