TESTING of Scottish pupils will not raise standards of literacy and numeracy, union leaders have warned.

Grahame Smith, general secretary of the STUC, said the Scottish Government should introduce smaller class sizes to improve attainment instead.

His comments came after First Minister Nicola Sturgeon announced that standardised testing for primary and secondary pupils was to be introduced.

The move came after the biennial Scottish Survey of Literacy found standards of reading and writing were falling despite the introduction of the Curriculum for Excellence, which was expected to raise basic standards.

Mr Smith told the STUC's women's conference: "Testing is not a policy that will improve attainment. The quality of teaching and the teaching environment will improve attainment, but politicians seem obsessed with testing because it is something that can be measured.

"Continually testing children does nothing to alter attainment unless it leads to more effective policy. Teachers know that smaller class sizes with support within larger classes will undoubtedly raise attainment."

"If pressure on resources means smaller class sizes across the board can’t be delivered in the short term, an excellent first step would be to reduce class sizes in identified areas of deprivation."

Mr Smith said politicians would be better off spending less time "obsessing about targets and measures" and invest more trust in the "competence and experience" of teachers.

In 2003, the former Labour-led Scottish Executive scrapped national testing because of the concern teachers had become overly-focused on "teaching to the test" rather than educating pupils.

As a result, the national survey of five to 14 attainment, which tested every pupil in primary school and the first two years of secondary school, was replaced by a system of scientific sampling to track the performance of a proportion of pupils.

The majority of Scotland's local authorities still use some form of standardised assessment to judge pupils' progress, but because they use different systems building a national picture of attainment is difficult.

An Audit Scotland report from 2014 found there were no comparable measures available at a council and national level on the performance of pupils from P1-S3.

However, standardised testing is controversial because opponents believe it leads to teachers teaching to the test and allows damaging league tables to be drawn up which compare schools serving different communities.