Far from the "marking chaos" which your article on November 6 alleges, the total number of level changes amounted to less than 0.3 per cent of the tests taken.
The marking of the science tests is deliberately rigorous, designed to give credit only where a pupil has shown the scientific understanding sought in the question.
Our marking agencies employ only experienced teachers of the subject concerned. The markers are trained thoroughly using exemplar scripts, and supervised carefully in their work, submitting examples of their marking to their supervisor.
The national tests are an open, transparent system. Marked test scripts are returned to schools so that schools can see what markers have done. Most markers are extremely competent; a few, sadly, are not. In the interests of schools and pupils we make sure the agencies do not offer further work to markers who fall below the standards required.
We continue to seek ways to improve the overall quality of the marking. The number of cases of poor quality marking does not call into question the overall reliability of the tests.
Head of curriculum and assessment Qualifications and Curriculum Authority 29 Bolton Street London