Sunday's child gets ready for the tests
The 30 11-year-olds from Taylor Road primary had also spent four mornings of their Easter holidays revising. Headteacher Christopher Hassall said parents had backed his preparation schedule.
He said outsiders "judged the performance of children and our school by their test results, despite the lack of a level playing field".
New figures from researchers who developed the tests suggest that pupils view them as more important than ever, and are working harder for them.
All national tests are tried out on a sample group of children before they are set for real. For example, the key stage 2 tests for 2000 were first tried out on some 1,300 11-year-lds in 1999.
The researchers - from the National Foundation for Educational Research - said that in the 1997 KS2 writing test, pupils who sat the "real" test only scored one more point (out of 50) than those who had taken the same test in a more relaxed context.
By last summer, the growing pressure surrounding the tests meant this gap had increased to 2.7 marks. However, although this pressure may spur pupils on, it has created extra stress.
Chris Davis, spokesman for the National Primary Heads Association, said one mother told him that her child had turned into a "nervous wreck" and had been physically sick several times the day before the tests.
The association is planning to survey schools and parents to find out what effect the testing culture is having on children.