Ofqual, the exams regulator, is to carry out more research into the quality of marking in national tests, it was announced this week as concerns emerged about the standards of assessment for this year's Sats.
The news came as the Qualifications and Curriculum Authority revealed it had managed to avoid a repeat of last year's debacle. It said 99.9 per cent of results have been delivered to schools on time.
In 2008, 1.2 million pupils had Sats results delayed in a shambles that led to the resignation of Ken Boston as QCA chief executive. It also resulted in the termination after one year of a five-year contract with ETS, the US company hired to adminster the tests.
However, the standard of marking remains an issue. Catherine Stoate, head of St Cleer Primary in Liskeard, Cornwall, contacted The TES after discovering that a marker of her pupils' English tests had failed to add marks from a long writing question into the final total. This means that all 32 pupils are a level lower than they should be in their overall English mark.
Mrs Stoate is furious that QCA says she must wait until September for the mistake to be corrected.
"I feel very distressed about this," she said. "The children haven't been told their results at a time when all other schools are getting theirs."
The head said she also had "serious issues" about the quality of marking in the English writing test.
QCA-commissioned research released in March suggested that only 55 per cent of pupils taking the English writing test in 2007 were correctly graded, prompting Ofqual to describe the accuracy of national test marking as a "significant cause for concern".
This year, rules were relaxed to let some markers with margins of error beyond QCA's normal acceptable limits to continue marking.
In some cases this was because flawed questions in dummy papers had led to good markers being artificially penalised. But as The TES revealed last month, leaked internal emails from Edexcel, the new contractor, revealed it was also deemed acceptable to relax the rules on markers' own mistakes. This week, schools received their results and were checking the marking.
Veronica Shaw, head of Scantabout Primary, Chandlers Ford, Hampshire, said: "This is the worst I've ever seen. We always send back a couple, except last year when we sent back five writing papers. This year we're sending back one overall English, six reading scripts all borderline level 45, four writing that are borderline 34 and seven writing that are borderline 45 out of a cohort of 33 children."
On the TES Connect primary forum, "Ballater6" said: "We have been really disgusted with the marking, some pupils with TA (teacher assessment) on level 3 have come out as high level 4s and others predicted level 5 came out average 4, when I have gone through them it seems the marker has given half marks for most of the writing, therefore clearly inaccurate."
"Sammiebullen" said all their Year 6 writing papers would be sent back: "Children writing good, well structured and correctly punctuated complex sentences getting 1 mark on sentence structure!"
Ofqual chair Kathleen Tattersall, said: "Ofqual is continuing to monitor the quality control of the marking of this year's papers, and we will be listening to schools about any concerns."