But some are critical of the government's handling of the system. The Key Stage 2 Sats exams are taken in Maths, English and Science by 11-year-olds and determine the school's place in the government's league tables.

King David Junior School head teacher Peter Parker is pleased that all his pupils attained 100 per cent at the benchmark level 4 in their Key Stage 2 Sats exams.

But he describes the administration of the exams as "tragic, inefficient and ineffective".

He vents his spleen on Educational Testing Services, the US-based company that the government has granted a £154 million five-year contract.

He adds: "This is the first year ETS has run the marking and clearly the government has given the contract to the lowest bidder."

KD Juniors received their results on the internet but they still have not received the papers to check on the children who are borderline between a level 4 and level 5 pass.

Mr Parker added: "I am disappointed that the children, teachers and parents have to face uncertainty as they wait for results to be validated."

North Cheshire Jewish Primary School head Norma Massel reports that her school also received perfect results. And she had the good fortune to have the papers back last week - exactly on time. But she admits that there had been "administrative problems" running the exams.

Bury and Whitefield Jewish Primary School head Christine Potter reported "no delays" in obtaining results.

But she was disappointed that the school narrowly missed perfect results because one child was just one point off a grade 4 in English.

She argues: "Marking English papers is subjective and down to the preferences of the marker."

But she was surprised to hear accusations that the marking company had used teenagers to mark the papers. She told me: "I'm a Sats marker and I've been marking as usual and received my normal training. All the other markers I met were suitably qualified."

Broughton Jewish Cassel Fox Primary School acting head, Shelley Caplan had no complaints about results or the way the papers were administered.

She said: "Our children passed level 4 in all subjects. All the papers came in last week present and correct."

Shadow children's secretary Michael Gove said: "The process used to make sure marking is rigorous and consistent has been deeply flawed and parents and teachers have lost confidence in the credibility of these tests as a result."

The government has launched an inquiry into what has gone wrong.