From the wonderful Michael Rosen.

High stakes, summative testing leaves no room for children or society to question the validity of reducing knowledge (and children) to people graded solely according to a right/wrong system of thought. They/we 'become' a grade that's based on this right/wrong way of thinking. And we are forced or conditioned to accept this grade as a final statement about ourselves - even though the test leaves much of who we are, how we think, how we work with others outside of the test, outside of the door. 

I find that if I query the basis of a question on a test, or a test as a whole, there is always someone who will come back and 'explain' that the given question is in fact 'reasonable'. (You can find an example of this on the comments thread following my article about using a poem for last year's KS2 SATs 'Reading' paper