One teacher expected three additional pupils from a class of 24 to attain level 2 - the average. In previous years they would have scored level 1, she said.
The change has been made to bring this year's tests into line with the new slimmed-down Dearing curriculum Orders, which take effect from September.
Teachers are happy with the change, which means children do not have to use a required number of full stops and capital letters to attain levels 2 and 3 if they meet other requirements.
However, it will make this year's results hard to compare with previous years', giving the illusion that standards have soared.
But Arthur de Caux, of the National Association of Head Teachers, says: "We take the view that all comparisons are meaningless while the requirements are changing, which they have consistently been doing."
Meanwhile, from 1996, level 1 in reading and writing will be harder to achieve, because the new curriculum Orders will bring the demands more into line with what can be expected of a below-average seven-year-old rather than a five-year-old.