But a batch of documents on the curriculum issued this week by Learning and Teaching Scotland shows that changes are at the embryonic stage. While many local authorities are reviewing their curriculum guidelines to make schools more attractive to pupils, relatively few had actually issued agreed guidelines.
Gordon Mackenzie, the former president of the Headteachers' Association of Scotland who chairs LTScotland's post-14 reference group, believes none the less that "more and more schools are looking at flexibility as a resource and are reflecting on what they can do to make education for young people more appropriate. There is definitely a momentum building up."
The inspectorate takes a cautious view, as it says schools themselves are also doing. At a conference in March on flexibility in the secondary curriculum, HMI noted that much of what it sees in the way of flexibility outwith existing national guidelines is the introduction of Higher Still programmes alongside or instead of Standard grade courses in S3-S4.
But inspectors are anxious about this development, suggesting that "the straight replacement of Standard grade with new National Qualifications may not always be appropriate in all subject and school circumstances".
The existing guidelines have allowed for flexibility for some time, equivalent to 20-30 per cent of the pupil week which schools can use to reinforce skills or provide additional work. But, in response to complaints that the curriculum was a strait-jacket which turned off many pupils, the Executive issued Circular 32001 two years ago which gave the go-ahead for authorities and schools to depart from the guidelines.
This was followed by a speech from Jack McConnell, the First Minister, in November last year in which official recognition was given for the first time that applying the same curriculum principles to the education of all children would disadvantage many.
Mr McConnell issued the mantra that "one size fits all" is no longer an appropriate approach and that has become the new curricular principle - repeated this week by Peter Peacock, Education Minister, in his foreword to the "emerging practice" document.
Last year, Mr McConnell declared that "the comprehensive system was never meant to be, and must not become, the excuse for a uniform system". He added: "The curriculum doesn't work for all our children - so why not maximise its flexibility?"
However, the LTS documents acknowledge a danger of fragmentation, which may encourage pupils to study subjects that do not cover a broad and balanced range. So the 2001 circular and HMI are agreed that flexibility "doesn't rule OK" (see panel).
Schools are not to be given complete latitude. "Balanced against the greater flexibility in the curriculum, there is concern that departure from long-established advice on the structure of the curriculum could lead to a fragmented approach to curriculum design and implementation, and the possibility of some pupils following entirely inappropriate curricula," states another of this week's LTScotland documents, on encouraging "professional reflection".
Mr Mackenzie agrees that "there cannot be a free-for-all". He added: "If schools are going to introduce flexibility, there must be a very strong rationale for it and they must show it is in the interests of young people.
And, something I believe is very important, they must involve pupils and parents in explaining decisions to them."
He said he would be unhappy if there was no rigour in a flexible approach.
"What you have also got to remember is that the present guidelines serve very many pupils very well indeed."
The "professional reflection" paper acknowledges that challenging questions are being raised "about the balance between providing diverse opportunities for pupils and ensuring that each young person's individual entitlements are safeguarded. Other questions relate to ensuring consistency in provision across the country if a system emerged that encouraged greater flexibility."
North Lanarkshire, one of the authorities which led the charge towards more choice for pupils, accepts that "continuity and progression" should remain key principles of the curriculum. But it says that the other main elements of "breadth, balance and coherence" need to be redefined. There ought to be a place for "relevance, choice, flexibility and innovation", the council says.
HMI remains on guard to ensure that some national policies, such as the controversial "entitlement" to a modern language, are not undermined by excessive flexibility. The inspectors say there is some evidence of pupils dropping modern languages at the end of S2 to take up courses in vocational and social skills.
Their message to schools is challenging. On the one hand, if HMI finds during an inspection that any key area of the curriculum has been dropped by a group of pupils, this will be "explored" with the school.
On the other, "passive unquestioning acceptance of existing guidelines will not find favour in inspection".
Flexibility in the Secondary School Curriculum: emerging practice and Focusing on Curriculum Flexibility in Secondary Schools: A Paper for Professional Reflection are the two LTScotland documents published this week along with Curriculum Flexibility (How Good Is Our School? series) from HM Inspectorate of Education.
A quick guide to flexibility
What is it?
* allowing pupils to study fewer Standard grades
* breaking the link between pupils' ages and their stage of schooling
* introducing vocational programmes in S3-S4, some along with further education colleges
* introducing Standard grade in S2 and allowing the most able to sit Standard grade Credit exams in S3
* replacing Standard grade with National Qualifications in S3 and S4
* introducing Intermediate 2Higher in December of S4
* allowing S2 pupils to study internally assessed National Qualification units
* online and distance learning, sometimes with colleges and universities How do you know if it's a good thing?
* has it led to clearly identifiable educational gain for pupils, based on a clear rationale?
* how effective was the consultation with parents, pupils and teachers before the changes started?
* is rigorous quality monitoring in place to evaluate the changes?
* how effective has implementation been?
* what arrangements are plannedto communicate the results?