There has been a "catastrophic slippage" in standards of science taught in schools, leaving children with a superficial understanding of chemistry, biology and physics, according to the Royal Society of Chemistry.

Declining standards in schools, linked to teachers focusing on test results rather than analytical skills, risks starving the country of vital skills, the RSC said.

In a competition run by the society, 1,300 pupils with a keen interest in science sat chemistry questions from O-level and GCSE papers set every decade since the 1960s. The questions were selected to test logical reasoning and problem-solving.

Only 35% got the toughest questions from the most recent GCSE papers right. But the pupils fared progressively worse when doing the older O-level papers. For the 1980s O-level papers, 23% of questions were answered correctly. On the 1970s papers, only 18% of answers were right and on the 1960s papers, just 15% of questions were answered correctly.

The government said the results merely demonstrated that science had evolved in 40 years, but Richard Pike, chief executive of the RSC, said: "The brightest pupils are not being stretched, or trained in mathematical techniques, because they can get a grade A* without doing a single calculation. Conversely, the majority get at least a 'good pass' – grade C – by showing merely a superficial knowledge on a wide range of issues, but no understanding of the fundamentals. A mark of 20% was sufficient in one of this summer's GCSE science examinations."

He said surveys had revealed that around half of independent schools have withdrawn GCSEs in mathematics and science subjects to opt for tougher, more traditional international GCSEs. The RSC is petitioning the prime minister to take action.

Michael Gove, the shadow children's secretary, said: "We've slipped 10 places in the international league tables for science, and children are being asked questions that show our curriculum isn't preparing them for the challenges for the 21st century. That's why we need to make sure that our exams are as good as the world's best."

A department for children, schools and families spokesperson said that standards in science were in fact improving in response to better funding of schools. "Times have changed – it is unlikely that pupils from the 1960s could answer questions set today, given that the role of science in society has changed so much in the last 40 years," she said.

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