Experienced markers of this year's Sats are still waiting for pupils' scripts, more than three weeks after the tests began. Many others have complained that they are unable to complete marking because batches of scripts sent to them appear to be incomplete.
ETS Europe, the company organising the marking, has also had to promise an unspecified amount of compensation to markers who are unable to examine, despite undergoing training, because scripts have not been posted to them.
The revelations raise fresh questions over whether test marking can be completed on time and to a good standard, with some experienced markers saying its organisation is the worst they have seen.
But Andy Latham, vice-president of ETS Europe, remains confident that results will be issued to schools on time and will be marked to a high standard (see right).
This year, for the first time, scripts are being delivered direct to markers' homes from ETS via parcel firm UPS, rather than being sent to their place of work by schools.
A key stage 3 English marker, leading a team of 10, said: "I still have no scripts to mark.
"In some ways I am probably one of the lucky ones. Markers in my team have received papers from schools which don't tally with their online information packages. They have been opened and resealed with brown tape, there are schools with groups missing, et cetera."
A key stage 3 maths marker, who is also leading a team of 10, described marking as an "absolute fiasco". He said: "I still have no papers. I was assured this morning that I would take delivery today and have therefore stayed in for 10 hours during one of my half-term days off.
"I honestly don't know if ETS knows where these scripts are."
Another marker, with four years' experience, wrote that he had 350 unmarked papers sitting in his study awaiting collection, after he had attempted to tell ETS Europe of his decision to resign.
ETS had not responded to his telephone calls and emails.
A KS3 English marker said she had asked for 650 scripts and received 970, of which all of one school's Shakespeare papers were missing. She had informed ETS, but there had been no reply.
Another team leader, with 29 years' examining experience, wrote of the "disgust I feel on behalf of all the pupils and teachers who are having their efforts torn to shreds by incompetents at the top".
Many experienced markers appear to have resigned this year, forcing ETS to set up a dedicated marking centre in Manchester for KS3 English.
In other subjects, it appears there are not marker shortages.
However, maths papers appear to be presenting particular problems, because markers have to enter every single mark at the computer screen. This amounts to 100 marks, or 40,000 marks for a teacher marking 400 pupils' papers.
Markers are asking to remain anonymous, as all have signed confidentiality clauses in their contracts. More than 4,000 postings about this year's marking have now been received on The TES website.
ETS's website said this week that it was possible that some markers would not receive any scripts.
David Gee, managing director of the National Assessment Agency, which oversees marking, said: "I'm disappointed that some team leaders do not have their scripts. They have historically been our best markers." He added that some of the problems had been caused by schools incorrectly bundling scripts to be sent back to ETS.
"We are talking about a small proportion of markers who have had a bad experience," he said. "The vast majority of markers have their scripts, and are actively marking and getting on with the job."
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'ALL RESULTS WILL ARRIVE ON TIME'
Andy Latham, vice president of ETS Europe, responds to the complaints
Since ETS Europe was appointed as the National Assessment Agency's delivery partner for test operations services for the 2008 national curriculum test cycle, we have implemented various new online processes for managing and monitoring the quality of the marking process.
These innovations include online 'standardisation', which tests markers' ability through the marking of sets of papers before beginning 'live' marking; and online 'benchmarking', undertaken throughout the marking cycle to ensure that markers are performing to the required standard. These results are used to mentor markers or, if necessary, remove them from the marking cycle.
These new processes allow us to collect comprehensive data on markers' performance against an objective national standard throughout the marking cycle.
Nearly 10,000 markers have been trained and have successfully completed the online standardisation exercise. The vast majority have now received their allocation of pupil test scripts and have begun submitting marks online.
Thousands more have already progressed beyond entering their first 80 sets of pupil results, and have successfully completed the first benchmarking exercise.
Another change we have introduced is to have markers enter the marks they assign directly online. This will provide to teachers electronic results for every question, removing a burdensome process often undertaken at a local level in schools.
The solution also ensures more accurate entry of results and sensitive data.
While the schools' administration of the tests went well, as with most projects, we have experienced some initial challenges in implementing our new solution. However, thanks to the co-operation of markers and dedication of the entire team, we are on track to complete a successful marking cycle this year.
Earlier this month, for a number of operational reasons, our ability to respond to communications to all markers accurately and in a timely manner was compromised. This caused frustration for some markers, for which I have apologised.
In a direct response, we have increased the number of customer service representatives and added additional phone lines to help ensure as many marker enquiries as possible are answered first time. In addition, we have created a dedicated team that is making steady progress in responding to all outstanding enquiries.
With the ongoing support of schools and markers, we remain confident that all schools will receive their results on time, marked to a high standard.
Photograph: Neil Turner
HOW THE PROBLEMS UNFOLDED
February 2007: ETS Europe, part of the US testing firm ETS, wins pound;154 million, five-year contract to mark national tests.
October 2007: Problems begin to emerge with an ETS pilot of new approaches to key stage test marking, forcing some senior markers to resign.
Early spring 2008: Teachers begin to report administrative problems, including ETS failing to register their contract details.
Early May 2008: Many teachers say they are still unaware of where crucial training is to take place.
Saturday May 10: KS3 marking training events are marred in some cases by markers failing to turn up.
Sunday, May 11: Computerised vetting system for KS3 English fails. It is fixed later in the week.
Friday May 16: TES front-page story reveals hundreds of complaints over test marking "fiasco".
Friday, May 23: Senior examiners tell TES of concerns about marking quality. ETS denies there are problems.
Sunday, May 25: ETS says it will offer compensation to markers who fail to receive any allocated scripts.