Two reports for The Wellcome Trust charity said the "high stakes" nature of tests led to the drilling of pupils rather than teaching for understanding.
The researchers said tests had a negative impact and called for a new approach to science teaching. The government said there was no evidence testing had a negative impact.
One of the reports, by Durham University's Peter Tymms - a long-standing sceptic about claims of rising standards - said many argued that school league tables based on national test results were harmful to education.
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