State schools in Scotland are cutting the number of exams pupils are allowed to sit, creating a “real danger” of an attainment gap with private schools, a study showed.

The number of National 4 and 5 tests that schoolchildren can sit has reduced sharply, according to research by think tank Reform Scotland.

A “minority” of Scottish state schools allow pupils to sit more than six exams, with some only offering five subjects, compared to independent schools that typically continue to offer eight or nine.

Children whose parents can afford to send them to private school or move within another school’s catchment area will be unaffected by this “unintended consequence of the Curriculum for Excellence”, director of Reform Scotland Chris Deerin said.

Calling for the Scottish Government to urgently address the situation, Mr Deerin added: “We are in real danger of opening up a new type of attainment gap in Scotland – one where children who are allowed to sit eight or nine National 4s or 5s will have a distinct advantage over those restricted to five or six, regardless of the latter’s ability.

“The schools cutting the number of exams on offer are typically those serving our more deprived communities, further limiting the life opportunities of children who may already be disadvantaged.”

Freedom of Information requests by the group revealed that, in 2016, all schools in Edinburgh, East Dunbartonshire and Dumfries and Galloway offered eight exams; now no schools in either East Dunbartonshire or Dumfries and Galloway offer eight, and the limit in Edinburgh varies between six and eight.

The implementation of the Curriculum for Excellence by the Scottish Government has been blamed for the reduction in available subjects, which critics say shows the “hallmark of poor management”.

Chair of the Commission on School Reform and one of the authors of Curriculum for Excellence Keir Bloomer said: “One of the purposes of CfE was to broaden pupils’ education, but instead the way in which it is being implemented is narrowing it significantly.

“There is ample opportunity for pupils to combine practical and academic options when they are enabled to sit nine, eight, or even seven exams, but when we narrow it down to six or five there is very little room for manoeuvre.

“Reducing the number of subject options is not a government policy. It has come about by accident; the unintended consequence of ill-conceived advice. This is the hallmark of poor management.

“This is a lose-lose.”

A Scottish Government spokeswoman defended the Curriculum for Excellence, claiming it “provides significant flexibility” and allows schools to “have the freedom to design a bespoke three-year senior phase of a range of courses and qualifications tailored to meet the needs of the young people at the school”.

She added: “What matters is the qualifications and awards that pupils leave school with, and not only what they study in S4.

“Almost two-thirds now leave school in S6, and last year a record proportion went on to positive destinations including work, training or further study.

“Young people also now have opportunities to study towards a much broader range of qualifications, not just at school, but also at college and through apprenticeships.”

Scottish Conservative shadow education secretary Liz Smith said: “This is yet further confirmation of the very serious reduction in subject choice which is affecting so many pupils across Scotland.

“It is a disgrace that the SNP has allowed this situation to develop, most especially when the evidence shows it hits hardest for those in the more deprived communities where the attainment gap is already a major issue.”