The education Secretary has been accused of evasion, vagueness and failure to provide enough detail about the new National qualifications for upper secondary.
In an ill-tempered clash at the Parliament's education committee, Labour's schools spokesman Ken Macintosh accused Michael Russell of avoiding questions that would be at the forefront of parents' minds.
The Education Secretary responded by accusing his Labour opponent of threatening the unity needed to make Curriculum for Excellence work.
Mr Russell also took a tough stance on incompetent teachers who cannot cope with the reform, stating that they should be removed from the classroom.
Would pupils start studying for their exams in S3 or S4, Mr Macintosh asked.
Mr Russell, making his first appearance at the Scottish Parliament's education committee in his new role, insisted that the Nationals marked a move away from courses with rigidly defined starting points and content, to a more fluid approach to learning. "The concept of you starting at this point is not a fair concept - there is a continual experience," he said. "You move into that and it will be tailored to the child."
The new qualifications would involve a "notional" 160 hours of learning, explained Mr Russell and Alison Coull, the Government's head of qualifications, assessment and skills. They could be taken over one or two years, although Mr Russell stressed passes by the end of S3 would be rare.
A dissatisfied Mr Macintosh continued to rail against the "alarming lack of clarity emerging in secondary school", and accused Mr Russell of failing to show leadership.
He forecast a "potential clash between the broad approach of the curriculum and a subject-led framework at secondary school", and said parents would be anxious to know the criteria for choosing subjects.
There would be "no change" to subject choice, said Mr Russell, who suggested Mr Macintosh refer his comments to the review of teacher education, being carried out by former senior chief inspector Graham Donaldson, and the CfE management board. He accepted Mr Macintosh might find this suggestion "inadequate", but the Labour MSP responded: "It's not the inadequacies but the patronising tone of the minister that I strongly object to."
He also accused the Cabinet Secretary, in a later press release, of being "evasive" over how much money local authorities would receive to implement CfE, and "vague" on what he would do about the absence of a parents' representative on the reform's working group.
Meanwhile, Liberal Democrat education spokeswoman Margaret Smith told the committee that some teachers were not up to the task of making CfE work.
Mr Russell agreed there were "some problems in classrooms that we need to solve", although the first step should be to offer support to struggling teachers. Where that did not work, "we need to be quite clear that these people should not be in our classrooms", he warned.
Incompetent teachers, page 31.