The Scottish Qualifications Authority (SQA) is coming under fire as teachers' fears grow over the implementation of the new National 4 and 5 courses.
Concerns have been raised that guidelines for teachers are confusing and that the help offered by the SQA is highly variable in quality.
Alan McKenzie, acting general secretary of the Scottish Secondary Teachers' Association (SSTA), said that teachers were "struggling" with Nationals, pointing to particular problems in science.
"That's a matter we took up with (education secretary Michael Russell) in a recent meeting," Mr McKenzie said. "He's very aware of the problems, particularly in physics where there seems to be little confidence in the verification process.
"Recent national training meetings have been a shambles. The issue has been conflicting advice from the SQA, and confidence around the NARs (National Assessment Resources) and materials to support the courses."
The SSTA will gauge members' concerns in a survey this month. The EIS teaching union is expected to reveal the results of its own survey on Nationals next week, while the NASUWT Scotland teaching union will address the issue in a broader survey on Curriculum for Excellence.
"We are not trying to say this is a disaster across the board but it has been more work than expected," said NASUWT Scotland president Mike Corbett. "There would be concerns about the quality of the people supposed to be applying standards and how they might go about their jobs. There is a lack of confidence in the process."
New Highers are due to begin in 2014-15, but Mr Corbett said there was an emerging view that a one-year delay would allow more time to get the qualifications established. "I can see a large number of departments saying `We want implementation of the new Highers next year'," he said.
Nick Hood, a teaching fellow at the University of Edinburgh, who runs the Scottish Physics Teaching Resources website, said: "My understanding of the situation with physics in particular is that there have been complaints about the information from the SQA arriving late, last-minute changes to course materials and information about assessment being unclear at best, or even contradictory.
"To find out how to assess National 4, for example, you have to read seven different documents concurrently - it's a nonsense."
Ken Cunningham, general secretary of School Leaders Scotland, acknowledged that the issues raised by the unions existed but said he was confident these would be "teething problems". Delaying the new Highers was likely to add to any confusion, he warned, as teachers would be dealing simultaneously with Nationals and two types of Higher.
Mr Cunningham added that every major change to qualifications was difficult but said that consensus across the profession marked out Nationals from previous reforms. "The preparation, consultation: there's been more than I can ever remember. The amount of effort that's gone into this knocks the others into the corner," he said.
Bruce Robertson, policy adviser for the Association of Directors of Education in Scotland (Ades), said that the SQA had "responded very well" to concerns over Nationals. The SQA, Education Scotland and Ades were together monitoring the implementation process on a weekly basis, he said.
Mr Robertson also strongly advised against delaying the new Highers: "I question whether it would be in the learner's interest to go from National 5 to the old Higher," he said.
An SQA spokesman said that the body had provided teachers with a variety of materials, including course arrangements for the new Nationals, and that in the past academic year it had run 140 National 3-5 subject events, attended by 7,486 teachers. A similar programme was to be run this year for the new Highers.
The SQA had listened to feedback from schools and teachers and considered "very carefully" where additional support was needed, the spokesman said. As a result, he added, extra continuing professional development around Nationals was being planned, although details were not yet available.
"Additionally, SQA is working with schools, colleges and local authorities to implement rigorous quality-assurance processes that ensure unit assessment judgements made by teachers meet the national standards," the spokesman said. "A training programme has been provided for those recruited as part of the verification process.
"To provide further support, feedback and further guidance from the first round of verification are being posted on the SQA website."