By Seonag Mackinnon
BBC Scotland education correspondent
Headteachers warned of a repeat of the exam chaos of 2000
Secondary headteachers have warned there is the potential for a repeat of the exam chaos in 2000 unless ministers rethink plans to overhaul the curriculum and exams system.
School Leaders Scotland (SLS), the heads' union, maintains the proposals are incomplete and seriously flawed.
The Scottish Government has billed its plans as the biggest education shake-up for a generation.
It said the SLS's concerns would be considered as part of its consultation.
School staff are broadly behind the idea of streamlining a curriculum widely seen as overcrowded, and an exam system that is often perceived as being eye-wateringly complex.
But many believe the government's reforms are sketchy and ill thought-out.
In a document submitted as part of the official consultation process, the secondary headteachers claim the changes are so complicated it will be difficult to draw up school timetables and assembly halls may be in more frequent use as exam halls.
It said: "SQA (Scottish Qualifications Authority) might struggle to be ready for the first diet [of exams] in 2012-13 and no-one wants to replicate the chaos of 2000."
Thousands of candidates received late or inaccurate results in 2000, which led to widespread criticism of exam body the SQA.
The headteachers maintain that the government's proposed changes may see pupils end up with less of a choice over the exams they sit in fifth and sixth year.
They also want youngsters to be examined in literacy and numeracy at aged 11, so they do not move up to secondary without a good grounding in the three Rs.
The heads also want pupils to have 18 months to prepare for Highers, and they have called for bright children to retain the option of sitting early exams which are normally taken in fourth year. This would offer them more time to prepare for Highers.
Ministers are proposing a new single exam to replace Standard Grades and Intermediate exams, two roughly equivalent qualifications normally taken in fourth year.
And they have also proposed literacy and numeracy exam for 15 year olds.
An SQA spokesperson said: "Since the plans for Curriculum for Excellence were announced by the Scottish Government earlier this year we've been developing a robust framework of procedures which enable us to support the implementation timetable announced then.
"The national consultation period over Curriculum for Excellence reforms and their implementation is about to end. All of the many points raised in the course of that consultation will go to the Scottish Government."
The Scottish Government said: "This is an open consultation and SLS have submitted their response which will be considered along with the other responses to the exam consultation which closes on 31 October."