The marking of England's national tests is in disarray because of administrative blunders, according to teachers involved in the process.
Many say they have quit as markers in protest at organisational mistakes surrounding key stage 2 tests, sat by primary pupils this week, and key stage 3 tests in secondary schools last week.
Blame is laid at the door of ETS Europe, an offshoot of a non-profit American testing company which is running the marking for the first time this year after taking over from the exam board Edexcel.
Senior markers have told The TES that it is unlikely marked scripts for key stage 3 English will be back with schools as promised by the end of term.
More than 1,500 angry comments have been posted by markers on The TES's online staffroom.
Many of their complaints relate to crucial training events which all examiners need to complete before starting work. Many said they had not been given information about the location of the training event, or had been asked to travel hundreds of miles at the last minute.
In addition, a computerised vetting process for KS3 English appears to have wrongly barred almost every marker from further work on Sunday and Monday.
Markers also said they were frustrated by ETS Europe's inability to respond helpfully to requests for information. One marker said she had never seen such problems since the introduction of the national tests. "We all deserve better than this fiasco," she said.
The difficulties will add to the controversy surrounding England's testing system, already under fire this week after a committee of MPs called for Sats tests to be scrapped in their current form.
All of the key stage 3 English papers are due to be returned by the end of term. But one experienced marker who leads a team of 10, and is in contact with other senior examiners, said: "I cannot see how this can possibly happen."
Initial training for KS3 markers took place on Saturday, straight after last week's tests, with KS2 events scheduled for tomorrow.
As late as Wednesday, some KS2 markers said they still did not know the location for their training.
The initial vetting process for markers of KS3 English was put on hold on Tuesday, with a promise it would be working later in the week, after the computer had rejected almost every marker. ETS was also forced to schedule at least one extra training event for KS3 markers on Monday, even though this a day when teachers have to work.
Andy Latham, ETS vice-president, said: "I apologise to all the markers who have experienced frustration with the training and the standardisation process.
"We remain firmly committed to our July 8 deadline for the delivery of the results."
David Gee, managing director of the National Assessment Agency, which oversees marking, said he was confident that it would be completed by the end of term, and that there were sufficient allocated markers in all subjects.
- What went wrong, page 6; Test complaints, page 8.
Join the online debate at: www.tes.co.ukstaffroom.