The new curriculum is intended to broaden pupils' learning
Teaching unions have stepped up their opposition to the implementation of the new Curriculum for Excellence.
Members of the ruling executive of the EIS, Scotland's largest teaching union, have voted to call for a work to rule.
They said the curriculum was only partially developed and would require large amounts of overtime from teachers to make it viable.
Meanwhile, the Scottish Secondary Teachers' Association has renewed its opposition to the new curriculum.
On Thursday, an SSTA representative at crucial talks with Education Secretary Mike Russell agreed to cease the union's opposition to the current implementation plans.
The decision followed assurances from Mr Russell that he was committed to making sure problems with the new curriculum were solved.
The SSTA executive has since distanced itself from its representative's decision.
SSTA general secretary Ann Ballinger said: "Our representative on the Board (Peter Wright) decided he had no choice but to accept the cabinet secretary's assurances after Michael Russell stated he was 'absolutely committed to make sure the problems are solved'.
"At its meeting on Friday 23 April executive reaffirmed its continued demands for a delay in implementation until teacher concerns are met.
"Following the meeting of the SSTA Executive today, the current and longstanding SSTA position was reiterated: there must be a delay in the introduction of CfE."
The new curriculum, which is already in place in primary schools and has been billed as the biggest shake-up in Scottish education for a generation, is intended to broaden pupils' learning.
It is designed to give teachers more freedom and make lessons less prescriptive, but critics believe it is not fully developed and that guidance about its implementation in secondary schools is sketchy.
Unions have called for a delay to the start of the new system in secondary schools.
A survey by the SSTA suggested that 89% of teachers wanted more resources before they begin teaching the curriculum in August and 78% said clarification of course content was essential.
However, an advisory board recommended that the new curriculum be introduced in the new school year, as originally planned.
The EIS union said its members had reported that secondaries were not ready to change to exam courses linked to the Curriculum for Excellence.
And the union's executive wants teachers to refuse to work more than the 35-hours a week in their contract.
But the EIS has agreed to enter into talks over their concerns with Mr Russell.
A Scottish government spokeswoman said: "The education secretary has invited the EIS to enter into constructive and detailed dialogue as early as next week to continue work to address their ongoing concerns about the new qualifications, which are not due to start for four years."
The EIS's final decision on industrial action will be taken by its annual conference in a few weeks.