Schools in England are "exam factories" due to ministers' obsession with league tables and targets, a National Union of Teachers conference has heard.
Children sit three sets of tests in the first nine years of education
And whenever schools fell short the government threw new policies at them, with head teachers counting 58 separate initiatives, academics said.
This had made it more difficult to find head teachers, with 60 teachers for every head in secondary schools.
The government said tests were a "non-negotiable part of school reform".
Education academic Professor Alan Smithers said despite extra investment the government had done "quite a lot of harm".
He said: "Unlike previous governments it has taken upon itself responsibility for 'delivery' through targets and pressure from the centre.
"Schools have been reduced almost to factories for producing test and exam scores.
"But scores are not the product of education in the way that cars, barrels of oil and tins of baked beans are for their industries; schools are there to benefit the children in them.
"It is an approach that has led the government to value only what can be measured."
He also claimed this "narrow focus" had led pupils who could not "make the grade" to become more disaffected and "our streets less safe".
In a study that the University of Buckingham academic carried out for the NUT, he found head teachers in state schools were able to recall 58 government initiatives they had been obliged to adopt.
These included changes in school organisations, the structure of schools and their status, workforce remodelling, personalised learning and vocational diplomas.
A spokesman for the Department for Education and Skills said it did not recognise the picture being painted and that Key Stage tests were here to stay.
"They are a non-negotiable part of school reform. They provide valuable objective evidence in the core subjects, helping inform further improvements to teaching and learning.
"This is an important part of our drive to raise standards in the basics even further in primary schools."
He added that they were not designed to be "pass or fail" examinations and that guidance stressed that preparation time should be kept to an absolute minimum.
There were three sets of national tests in the first nine years of education in England, he said.
And the four years of Key Stage 2 between seven and 11, tests represent just 0.14% of the available teaching time.
"This small commitment is vastly outweighed by the benefits of the information provided to teachers, parents and pupils," he added.