Kathleen Tattershall, chief executive of the Northern Examinations and Assessment Board, believes that placing children into "academic", "vocational" and "work-based" categories at an early stage could give pupils less choice than ever.
Addressing the annual conference of the Historical Association at York University she said that GCSE and A-level could become "academic ghettos" with the three pathways perceived as little more than gradations of desirability.
Ms Tattershall was particularly concerned that A-level subjects may be separated by the different pathways, with some - like history - becoming the preserve of an elite. On the other hand, subjects like business studies would be confined to the purely vocational route.
"Are we in the business of making it possible for people to have a flexible approach across different kinds of curriculum experience? If so, how do pathways contribute without locking people into a particular route?" she asked this week.
"If students embark on the wrong course they should have the opportunity to transfer - while being credited for the work they have already done.
"My concern is that the links between the pathways will not be there in practice. That there will be a lack of choice. And that we end up with less flexibility than at present. There's a real danger that the pathways will become no more than gradations of desirability."
Sir Ron's report, published earlier this year, attempted to make sense of the existing divisions within education. He outlined a route based on A-levels, one centred on GNVQs; and a pathway based on training in the workplace. He hoped that by placing them in a single structure they would be seen as equally valuable.
Ms Tattersall said that the first priority is to agree the ground rules of the whole system. She believes there is a danger that the "key skills" placed at the heart of learning by Sir Ron Dearing will be interpreted differently for the different types of learning.
She also believes that parity of esteem is impossible unless GNVQs are subject to the same examination regulations as A-levels. Exam boards like her own have been angered by Government plans to restrict the number of re-sits for candidates in modular A-level courses; there are no plans to treat modular GNVQ candidates in the same way.
"The structures that should be there to affect national policy in this regard are lagging behind," she said. The merger of SCAA and the National Council for Vocational Qualifications has not yet been formally announced so there is still no co-ordinating body.
"We are in danger of failing because course content remains insufficiently common across the pathways.
"We are in danger of failing because the regulations governing the framework are insufficiently coherent."