Schools in poorer areas are cutting the number of qualifications pupils can go for, research has revealed.

A study by policy group Reform Scotland found the maximum number of National 4 and 5s offered in fourth year can vary from five to 10.

More state comprehensives are limiting subject choice compared with fee-paying schools in a move that risks creating a new attainment gap.

Keir Bloomer, a Reform Scotland board member who helped design the current curriculum, said: “Parents, many of whom will have had the opportunity to sit eight Standard Grades, will not understand why their children are facing a narrowing of subjects.

“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.”

East Renfrewshire, one of the top-performing areas, allows children to sit eight or more exams. In East Dunbartonshire, the cap is seven.

Aberdeen schools offer six while those in neighbouring Aberdeenshire offer between six and eight. In Argyll, it varies from just five in Islay to nine in Oban.

Dundee schools all offer six, while in Edinburgh it can reach eight. Glasgow City Council said it doesn’t hold the information centrally.

Independent schools offer from eight to 10.

Reform Scotland director Chris Deerin said: “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.”

The Scottish Government said the Curriculum for Excellence provides “significant flexibility”.

A spokeswoman added: “Wherever possible, schools should ensure that young people can choose their preferred subjects in the senior phase, working with partners to do so.”