TENS of thousands of school pupils in Scotland are failing to master basic literacy and numeracy skills by the age of 14, according to new figures.
Standards in either reading, writing or numeracy among pupils about to embark on Standard Grade courses fell in more than half of local authorities last year.
Among the worst performing areas were Glasgow, Midlothian, East Ayrshire and Clackmannanshire.
The figures, obtained under Freedom of Information legislation, are based on assessments made by each local authority as to whether pupils have achieved basic skills in reading, writing and numeracy - defined as a level E score - set by the Scottish Executive.
The results show that in 17 of the 30 local authorities that provided data, standards in at least one of the three subjects declined. In five local authorities, standards declined in two of the three subjects.
In one council, Stirling, standards declined in all three areas.
The Headteachers' Association of Scotland last night admitted that attainment levels at S2 were "a concern".
Bill McGregor, the general secretary, said he hoped an ongoing curriculum review would drive up standards of literacy and numeracy.
"It's generally recognised that attainment at the end of S2 is a problem.
"I'm sorry there's been a decline from last year, but you have to look at a whole series of years to get the true picture.
"The concern is that there is a long-term issue here and the curriculum for excellence that is currently being worked on is taking this very seriously indeed."
It is widely believed that the transition from primary to secondary school is contributing to poor S2 attainment levels, and Mr McGregor said more so-called "transition teachers", who have worked in primary schools, are being employed in secondaries to smooth that process.
"Hopefully the combination of transition teachers, who can bring their methodology with them into secondaries, and the curriculum for excellence, will make a real difference."
Earlier this year, ministers revealed they were dropping their target of ensuring all S2 classes have a maximum of 20 pupils.
Opposition politicians said the figures were a serious setback for the Executive.
Fiona Hyslop, the SNP's education spokeswoman, said: "
At a time when the class size target for Maths and English in S1 and S2 is not yet being met, it is deeply concerning to learn that this is impacting on young people's ability to meet basic standards of literacy and numeracy by the age of 14.
"We need to give teachers space to teach the basics of literacy and numeracy, as schools are being overwhelmed with too many government initiatives."
Murdo Fraser, the deputy Scottish Tory leader, said: "These are worrying statistics and devastating news for Jack McConnell.
"Eight years into a Labour/Liberal coalition and we are still seeing deteriorating standards among our youngsters despite large injections of taxpayers' money into the system."
Glasgow council said standards in the city's schools had risen since 2004.
"Figures in isolation do not reflect the true picture as many factors have to be taken into account," said a spokesman.
The Scottish Executive said: "There has been a steady improvement in pupils' achievements at all levels in the past decade, including at level E."