Markers are threatening to quit over a behind-the-scenes "shambles" over the organisation of tests for 11- and 14-year-olds this year.
With the key stage 3 tests due to start on Tuesday, examiners have been bombarding The TES online staffroom with complaints.
Many markers say that they still do not know the location of compulsory training events the weekend after next, a crucial first stage in the marking process. However, as The TES went to press, ETS, the American company running marking for the first time this year, promised that training event details would be released from today.
The markers are also unhappy about a new system of entering pupils' results, in which they will have to record each mark a pupil scores for each part of each question at the computer screen.
There are also complaints about telephone calls telling markers they were selected to mark one subject, when their contracts told them another. There are also complaints about other administrative mistakes. The reported problems affect both the key stage 2 and 3 tests.
One key stage 3 marker said: "It appears that this year's key stage 3 marking process has become a complete shambles.
"Markers do not know as yet where they are marking, what schools they are marking or how many scripts they are marking. No one has any information."
Andy Latham, ETS Europe's vice-president, said that the company had decided to wait until a series of meetings with senior markers last weekend before allocating rank-and-file examiners to particular training events.
This had now happened, and key stage 3 markers would be given details of their training by today, while key stage 2 examiners would be told by next Thursday.
Dr Latham added: "I completely understand why people in the field would be nervous, because someone new is coming in and a number of changes are in process.
"But these are designed to make the marking process better."