Children from the wealthiest parts of Scotland are already 14 months ahead of their peers from poorer neighbourhoods when they start school, according to research involving almost 20,000 children.

The Performance Indicators in Primary Schools (Pips) figures on P1 children, who usually start aged 5, also shows that progress in school over that year varies widely depending on which school a child goes to, by as much as 12 months for reading and 14 months for maths.

Save the Children’s head of Scotland, Neil Mathers, was shocked by the “gaping chasm” in educational development between children from the most and least deprived areas.

“Too many of these children will start school struggling to learn and never catch up,” said Mr Mathers, who called for investment in the early years to narrow this “inexcusable gap”.

The figures were published quietly on the same day that first minister Nicola Sturgeon confirmed her government would press ahead with controversial plans for standardised testing in P1, P4, P7 and S3. The tests are designed to kick-start efforts to close the achievement gap.

They will be introduced in 2017 after pilots later this year and, according to Ms Sturgeon, will “provide better and more consistent data about our children’s performance than we have ever had before”.

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