Researchers at King's College, London, have found that 14-year-old kids these days are only as bright as the average 12-year-old used to be way back in 1976.
The reason behind the decline in intelligence has been attributed to the fact that children these days spend more time playing video games and watch television, instead of doing practical activities to boost their brains.
However, the findings go against school exam results, which have seen a steady rise in grades across all age groups.
Prof. Michael Shayer said that his research, involving 800 youngsters, showed that they were being "dumbed down".
"The moment you introduce targets, people will find the most economical strategies to achieve them," the Daily Star quoted him as saying of school assessments.
But the Government insisted last night that it was "driving up standards" in schools.
"Good teachers do not need to teach to a test," a spokesman for the Department for Children said.
"We have already taken steps to reduce the testing burden, but targets and testing are integral features of any work to drive up standards," he added.