Gordon Raggett CEO of Christian group, Cribs Charitable Trust works in Bexley in primary and secondary schools and told Premier's News Hour testing is not always the answer.
He said: "I think we need to move far more towards giving professional teachers more scope, more weight, more resources to assess pupils themselves.
"They're the ones after all who know their pupils really well, I think they do it really well."
He was speaking after 7-year-olds Sats primary school spelling test had to be scrapped when it was found they were published online by accident.
The test paper was accidentally published on the Department for Education's website and the government's been forced to cancel its new spelling and grammar test.
Gordon Raggett said that sometimes testing can do more harm than good: "We see evidence of highly stressed children, who are very worried about testing, especially in our borough, London borough, where we have a selection system so there's even more pressure on children."
He went on: "There's an argument that says lots of testing has a negative effect on children's learning - it demotivates them.
"What they learn to do is get strategies that help them past tests, rather than increasing their understanding and their abilities."
Half a million seven-year-olds in England had been due to take the tests next month, as part of their Sats.
Head teachers' leaders had called for the test to be scrapped before the blunder.
The Key Stage 1 test results, by children aged 7, are used by teachers to reach an overall judgement of the standards pupils have reached in these key subjects.
Listen to Premier's Marcus Jones speak to Gordon Raggett here:
