As part of a study of key stage 2 results academics questioned primary teachers as their former pupils joined a comprehensive school.
"Our teacher assessments represent a much more accurate profile of a pupil's academic ability," said one respondent.
Another agreed, adding: "We use the test levels to confirm our own assessments."
The study, conducted by Rosemary Davis, an academic at Oxford Brookes University, and David Rolfe Hopkins, a teacher, also found that key stage 2 tests create stress for both teachers and pupils.
"We're rushed off our feet... our pupils leave feeling exhausted," said one teacher.
Most had also detected a steady decline in pupils' long-term memory. Several attributed this to teaching methods that cater for the short-term demands of national tests.