CHILDREN across Scotland should not start formal schooling until they are six or seven, the leader of the Scottish Liberal Democrats has said.

Willie Rennie will use his speech at the party’s autumn conference today to call for a major shake-up of the way four and five-year-olds are taught.

He will also say the LibDems will “stand with” parents and teachers if they choose to boycott controversial tests for primary one pupils.

A spokesman for Education Secretary John Swinney branded this pledge “reprehensible”, insisting: “School assessments have been used in Scotland for years.”

Mr Rennie will argue children were historically sent to school early so that "mothers could provide cheap labour in factories”.

He will add: “It wasn’t for the benefit of the children but for the profits of unscrupulous bosses. Almost nine out of 10 countries in the world start formal education at the age of six or seven. Only a tiny fraction join Britain at such an early age.

“That’s why I want Scotland to join the majority of countries around the world. I want schools be able to change the way we teach children aged four and five.

“We should start formal schooling at six or even seven. I want children in Scotland to get the long-term educational benefits.”

The call received a mixed reaction from other parties. The Tories noted there is “interesting international evidence which points to very successful education systems with a later start than is the case in Scotland”.

But shadow education secretary Liz Smith said these nations “tend to have very different structures for both childcare and general taxation”.

Scottish Greens education spokesman Ross Greer said the party had “long believed formal education should start at seven, as it does in the countries which regularly top the global league tables for both education and child happiness”.

Countries such as Finland, Estonia and Switzerland all have a kindergarten stage for three to seven-year-olds, with an emphasis on outdoor play and creativity.

However Eileen Prior, executive director of Connect – formerly the Scottish Parent Teacher Council – warned introducing such a system in Scotland would be a massive logistic challenge.

She said: “Change is not easy for anyone, and I think we can see that – some of the changes in our education system have been very difficult.”

The EIS, Scotland's largest teaching union, said it was currently investigating the "opportunities and challenges" associated with changing the school starting age.

A spokesman added: “Other countries whose children start school later have universal pre-school provision, something we don’t have in this country."

Mr Rennie will use today's conference address in Dunfermline to attack Scottish national standardised assessments, which have been criticised by teachers.

He will say the LibDems would back parents and staff who boycott the literacy and numeracy tests, aimed at helping teachers judge a child's progress.

Mr Swinney announced changes to assessments last month after hearing feedback, but opposition parties want them scrapped.

Mr Rennie will say: "International evidence shows that the under-sevens need a play-based approach to learning with plenty of opportunities for active, outdoor, social, self-directed play.

"National testing, especially for five-year-old primary ones, pulls Scottish education in exactly the opposite direction."

He will warn the minority SNP Government that opposition parties would defeat it in a vote against the tests, adding: "At that point if the pupils, parents and teachers boycott these tests, we will stand with them.”

A spokesman for Mr Swinney said: “This is deeply irresponsible from Willie Rennie. For the sake of a cheap party conference speech line, he wants to threaten the future of children’s education. That is reprehensible, even for the Lib Dems.

“School assessments have been used in Scotland for years. Twenty-nine of Scotland’s thirty-two councils had them before the national scheme was introduced – including many Lib Dem-run councils – and, unlike the new scheme, the majority assessed P1 pupils twice.

“Throughout that time we didn’t hear a peep from Willie Rennie. It would appear he only discovered he was against school assessments when a new version was introduced by the SNP Government. This is perhaps the worst example of Lib Dem hypocrisy we have seen in recent times.”