Half of Scotland's councils have scrapped smaller class sizes for English and maths in early secondary or are considering doing so, The TESS can reveal.
A survey of all 32 local authorities has found that 13 have abandoned the target of maximum class sizes of 20 pupils in S1-2 for English and maths, while a further three are considering dropping it. The remaining 16 continue to honour the target.
The move, attributed to authorities' need to cut budgets, was branded a "retrograde step" by teaching unions and the Labour Party. The LabourLibDem Scottish Executive introduced the target in 2004 and it was implemented in virtually every local authority.
Access to smaller class sizes has now become a postcode lottery, claimed Ken Cunningham, general secretary of School Leaders Scotland.
"The scrapping of this target is not universal, emphasising once more the inequality of education provision that exists across the country," he said. "Where you are will depend on whether you get access to smaller class sizes; that's simply not fair."
Research into pupil achievement and attainment has consistently shown that a greater proportion of pupils reach expected levels in key subjects at primary than in early secondary.
It was for these reasons that in 2003, Scottish Labour pledged to reduce the then class average of 26 in S1 and S2 English and maths classes to 20, said Des McNulty, Labour's shadow education secretary.
"This policy was driven by the dip in attainment in S1 and S2," he said. "It was there that HMIE said we needed to focus resources and we listened. We've had three years of cuts in education and now we're getting to the point where real damage is being done. Moving away from this policy is a retrograde step."
Smaller classes in S1-2 have led to a "dramatic" improvement in the numbers of pupils hitting the appropriate 5-14 levels in English across Glasgow, said Larry Flanagan, who is principal teacher of English at Hillhead High, as well as education convener of the Educational Institute of Scotland and a member of the Curriculum for Excellence management board.
"The policy has been more than vindicated by improvement in terms of literacy," he said. "Most of my teaching career has been spent in class sizes of 30 - the dynamic in the classroom changes quite dramatically."
A Scottish Government spokesman said while class sizes of 20 in English and maths were desirable, it was up to local authorities to decide whether or not this was a priority.
"Research consistently shows that class size limits have the biggest impact on the early years of primary school and that is where we are concentrating our efforts," he added.