apparently in Kent it happens most often with nvr
Understandable, given a large block of answers, all A - E in identical little boxes, differentiated only by the question number. The child would be concentrating so hard on trying to get the right answer, under pressure and working against the clock, that they could easily start putting the answers in the wrong boxes.
In the Bucks test instructions, children are told not to guess answers
. They are told to come back later if there is time and answer any they have missed, but as we know, leaving a gap (rather than guessing at the time and correcting
it later) would make getting out of sync a distinct possibility, especially for answer sheets with this layout.