In the new single level tests being piloted in English reading, English writing and mathematics, the questions are all pitched at a certain level of understanding.

BBC: All school Sats tests 'might go'

Last year's figures showed 77% of 11-year-olds had reached the required standard in English - comprising both reading and writing - up from 75% in 2003.

BBC: Critics say nationwide school tests are too stressful

English comprises tests for reading and writing - and if reading is looked at separately, 54% of girls and 41% of boys across England are at this level.

BBC: What do Sats test levels mean?

Examiners will struggle too, to produce a single test that measures the same level of ability in children of different ages. (In music tests all candidates for a given grade play the same pieces: in an English test, quite different reading texts and writing topics would suit an eight-year-old than an 11-year-old.) The changes might even have the perverse effect of making children sit more tests.

ECONOMIST: School examinations

Comparing dyslexics in various countries, they found that English-speaking dyslexics experienced far more problems with reading and writing than the others.

BBC: Scientists find cause of dyslexia