In the United States, classes had been cut in states such as Tennessee. The Scottish public also wanted smaller classes but ministers were failing to publish concrete plans in their response to the national debate on education.

“It is a cruel hoax on the people of Scotland after a so-called great debate to produce a document which is as empty of solutions as this. People have asked for bread and have been given a stone in terms of this document,” Mr Russell said.

He appealed for vastly reduced classes in the first three years of primary where investment would bring the greatest return. SNP policy is to cut classes to 18 in these years as a first step.

But Labour, Liberal Democrats and Tories rejected any radical class size cut, although Nicol Stephen, Deputy Education Minister, again promised reductions in maths and English, most likely in the first two years of secondary. “We are committed to reviewing class sizes across all critical stages and will be bringing forward proposals to make reductions where they matter most,” Mr Stephen said.

He opposed a “single monolithic policy” of cuts between P1-P3 which would have a massive knock-on effect across the rest of primary. Many schools would need an extra five to seven classrooms.

Brian Monteith, the Tories’ spokesman, described the SNP’s demand as “unworkable and undeliverable”. Many schools were already overflowing, particularly in the Dunblane and Perth areas.

“The simple truth is class sizes of 18 or fewer cannot be delivered without effectively abolishing placing requests, tearing up the current catchment areas and in many cases building extra classrooms or even new schools,” Mr Monteith said.

Karen Gillon, Labour convener of the Scottish Parliament’s education committee, said cuts were “unachievable” and adult-pupil ratios were already being cut with the advent of classroom assistants.

Mr Russell also attacked the Labour-Liberal Democrat record on education over the past four years, accusing the coalition parties of failing to hit their improvement targets.

By the time pupils left primary, 28 per cent failed to reach their target in reading, 41 per cent in writing and 32 per cent in maths. The gulf in Standard grade performance was now wider between the advantaged and disadvantaged than it was when the parties took power.

“That is the gap between rhetoric and reality,” he said.

The Executive also came under fire for allowing companies such as Amey, the key player in the public private partnership (PPP) schemes in Glasgow and Edinburgh, to make a 31 per cent profit worth pound;13 million before it sold its interest to another company.

Tricia Marwick, SNP, said PPP schools were so far failing to meet the highest design standards for modern learning. It cost pound;18 million more every year to refurbish schools than under conventional public funding.

* Colin Campbell, SNP, a former Glasgow secondary headteacher, who was making his final education contribution in the Parliament, said that heads were still finding it difficult to convince staff to accept change, were often isolated and were the subject of orchestrated campaigns. They could be hit by a succession of grievances to which unions sometimes signed up.