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, while independent schools that typically offer eight or nine.
Details released under Freedom of Information revealed that in 2016 all schools in Edinburgh offered eight exams; now the limit varied between six and eight.
In East Lothian pupils are limited to seven exams where previously they were allowed to sit up to eight. In West Lothian, Deans Community High School had moved from eight to six. Midlothian did not provide figures.
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.”
He said children whose parents could afford to send them to private school or move within another school’s catchment area would be unaffected by this “unintended consequence of the Curriculum for Excellence”.
Scottish Conservative education spokeswoman Liz Smith said the figures were confirmation of a serious reduction in subject choice for many pupils.
Scottish Labour’s Iain Gray said teacher shortages were also narrowing subject choice.
Edinburgh’s Green education spokeswoman Mary Campbell said there was a distinction between the number of exams young people sit and the number of choices they have from which to pick those subjects.
“The intention of the new curriculum was always to reduce the number of exams in fourth year, from, say, eight under Standard Grade to six under Nationals. It’s about less quantity and more quality and reducing the gulf to Highers.
“However, whatever the number of qualifications, young people still need to have as wide as possible a range of choices to pick from. There is still a lot of work to do on that, with students at smaller schools sometimes facing fewer choices.”
Edinburgh’s FoI response said: “There is no limit set centrally. Schools choose the best structure for their own context. Even when schools on paper may set a limit, in terms of the number of subjects timetabled during the school day, there may be individuals who do other courses as self-study, or in non-school hours.
A Scottish Government spokeswoman defended the Curriculum for Excellence, claiming it “provides significant flexibility” and allows schools “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”.