A “narrowing” of the curriculum is limiting the range of subjects on offer and potentially also young people’s options after they leave school, they said.
Holyrood’s Education and Skills Committee heard from several experts on the 2018 examination entries and the way Curriculum for Excellence (CfE) is working.
Under the old system, most pupils studied eight subjects in S4. Now, according to Professor Jim Scott, an honorary professor of education at the University of Dundee, schools are offering anything from five to eight courses under the new curriculum.
Prof Scott, who surveyed all 359 secondary schools in Scotland, said: “The latest position is that 54 per cent of Scottish secondary schools are offering their children only six courses.
“Approximately a third, slightly less than that, are offering seven courses. About an 11th are offering eight courses and there are still three or four hardy souls who are offering five courses.
“The evidence demonstrates that the problem for many middle and upper ability-ranged children is that their choice is being squeezed, particularly in the five and six-course schools.”
Children in those schools tend to take maths and English then two sciences and a social subject, or vice-versa, leaving “the entire remainder of the Scottish curriculum” fighting to be the final subject.
“Needless to say, much of what would have been a beneficial experience for these children in times past has gone and that obviously has an impact on attainment,” the former headteacher added.
Prof Scott said there would have been an “almost unbelievable” extra 622,000 qualifications in Scotland since 2013 if these changes had not occurred.
“That curriculum narrowing has both impacted significantly on the quantity of attainment, but also on the progression pathways then available to children,” he said.
Dr Marina Shapira, from Stirling University’s social policy department, said she also found a variation in the number of subjects offered to S4 pupils across different councils.
“Our findings were quite striking because we found a clear relationship in the rate of reduction of the number of subject choices made by S4 pupils and the level of school deprivation. This finding is very worrying.”
Labour MSP Johann Lamont, deputy convenor of the committee, said the idea of young people having fewer chances in poorer areas than they had five years ago was “deeply troubling”.