They will demand that the first paper, which was scrapped after questions were leaked to a handful of schools, should, after all, be taken into account for some pupils.
An application for leave to seek a formal judicial review is due to be launched in the High Court this week. If successful, it is expected to lead to a flood of tribunal appeals which could throw the transfers from primary to grammar and secondary intermediate schools into chaos.
Leading Belfast solicitor Patrick Donaghy confirmed a number of parents from across the Province are prepared to initiate a test case. "Some of them said their children did well in the exam which was scrapped, which was deemed to be a difficult paper, but did poorly in the substitute paper," he said.
"Others had children who obtained A grades some years ago and were expecting similar results for their other children but found they had obtained Ds. They want to know what happened."
He said the papers from the scrapped test had been kept and the marks could be compared with the results of the re-sit.
Education minister Michael Ancram ordered a complete re-run of one of the two tests last November after evidence that some pupils had seen a number of questions on the paper in advance.
Ulster's Department of Education has said it cannot comment pending the outcome of a judicial review. The legal process is expected to take some months.