THE Scottish Government has been accused of a "decade of failure" in education after schools recorded their worst ever performance in a leading international pupil survey.

Scotland's scores for reading and science declined in the latest Programme for International Student Assessment (Pisa) while performance in maths was stagnant.

It was the first time since the tests began in 2000 that all three subject areas were classed as "average" with none "above average".

Read more: Scottish school standards in science and reading slump in damning Pisa survey

Opposition parties said the results showed ten years of failure under the SNP with First Minister Nicola Sturgeon previously saying she wanted to be judged on her record on education.

Sir Michael Wilshaw, England’s outgoing chief inspector of schools, accused Scotland of "dragging down" the UK average because of its poor performance.

The current head of Ofsted said: "Scotland used to be the beacon of excellence – it’s not any more. England is overtaking Scotland. The Scottish Government has got to focus on the basics in a way our education system has focused on in the last few years."

However, teachers called for a period of stability blaming cuts and the turmoil of the introduction of the Curriculum for Excellence, which has seen an explosion of school bureaucracy and unnecessary assessment.

Liz Smith, education spokeswoman for the Scottish Conservatives, said: "The fact the SNP has been so obsessed with independence has meant it has taken its eye completely off the ball when it comes to education.

"Nicola Sturgeon says she wants to be judged by her performance on education, but parents will rightly wonder what on earth her Scottish Government has been doing for the last 10 years."

Read more: Scottish school standards in science and reading slump in damning Pisa survey

Iain Gray, Scottish Labour's education spokesman, said the SNP should be "ashamed" and called on John Swinney, the Education Secretary, to apologise.

He added: "For all their warm words about making education a priority we are seeing performance going backwards as Scotland drops down international league tables."

Mr Swinney said the statistics were "unacceptable", but said they underlined the case for radical reform of Scotland’s education system.

"The results undoubtedly make uncomfortable reading, but they contain a plain message that we must continue to make the changes that are necessary to strengthen Scottish education," he said.

"It is by carrying through on these reforms, no matter how controversial, that we can make Scottish education world-class again and this requires an unwavering focus on improving Scotland’s education system."

However, councils argued that local authority control of education was effective in both educating and supporting pupils.

A spokesman for council umbrella body Cosla said: "Whilst it is disappointing Scotland has fallen in the rankings it has to be recognised that this is only one measurement.

Read more: Scottish school standards in science and reading slump in damning Pisa survey

"There is nothing in these results that suggest a change of governance will lead to improvement in these particular curricular areas."

Andreas Schleicher, director of education for the Organisation for Economic Cooperation and Development, which compiled the tables, said Scotland's results were a "surprise" given the school reforms undertaken.

He said: "I would have hoped and expected that some of the efforts they have made would have come out. But in the data there is no evidence, rather the opposite."

Hugh Aitken, director of CBI Scotland, said the success of the Scottish education system was a shared challenge for schools, government and employers.

He added: "We continue to recommend devolving more control to schools to empower teachers and school leaders to make curriculum for excellence work, and further action to open up the teaching profession."