Primary and secondary schools around the country have complained about the English results at both 11 and 14, saying the marking was too hard or inconsistent.
Of the 34 markers surveyed by London University, 32 said they double-checked with their supervisor if they were at all in doubt about what mark to give.
But 19 out of 30 primary heads from another part of the country said they were disappointed or unhappy with the English results and five were appealing to have scripts remarked.
"In fact, one head spent Pounds 300 to pay a teacher to mark everything again - they had found so much wrong with the marking," says researcher Bet McCallum. "In 25 cases it made a difference to the final level. The head wants everything re-marked by the exam board."
She says that as reasons for test marks being lower than teacher assessment, heads blamed either the criteria ("the poorer children got level 4 and so did the bright ones", said one); the tests themselves or the markers.
Of the 15 heads who had scrutinised the scripts, five had "found the marking reasonable". Twelve heads had not scrutinised the marked scripts because teachers' workloads were heavy enough, and in any case the results were not "high stakes", particularly since children had already been allotted to secondary schools.
Ms McCallum writes: "The criteria for English (particularly story-writing) were indeed quite strict and did not include extra marks for 'ingenuity', 'imagination' or 'vision', as some teachers and heads would have wished, and for which they themselves might have given recognition in teacher assessment. External markers in this sample conscientiously stuck to the criteria given and, if in doubt, had marks double-checked by their supervisors."
Most of the external markers found the work challenging, and said they would apply to do it again.
The Government brought in external marking for the first full national run of tests for 11 and 14-year-olds because of union pressure about workloads. The exam boards involved in GCSE and A-levels were appointed to hire thousands of markers to carry out the work. They were arranged in a hierarchical structure, from chief marker down to senior markers, markers and clerical checkers, with more levels in between. Markers had 10 sample scripts checked before continuing, and "in addition, markers were constantly telephoning supervisors for advice on marking pupil responses which did not fit neatly with the SCAA criteria", says Bet McCallum.
The markers in the survey were mainly teachers, including part-time, supply and retired teachers. Most took on the work for the extra money, but there were other reasons: to compare children's work; to learn more about how to judge children's attainments and to learn about progression (in the case of infant teachers).
The work required a great deal of concentration, and most said it had "taken over" their lives for a month. Some lost sleep "worrying if I'd got it right".
Although fewer than half the markers said they had found the marking enjoyable, all but five said they would apply again next year. Those who enjoyed the work said it was "challenging, the children's work was often 'astoundingly good', their expectations of what children could do had been raised, they had gained insights into children's thinking".
Another eight were ambivalent, saying the work had been rather intensive and stressful, and scripts could be monotonous. Ten did not enjoy it at all. It had been time consuming and had caused too much stress and worry. "For two teachers, the depressing content of most children's stories ('horror, social deprivation') had been quite disturbing."