The cost and number of exams that English teenagers take will soar even higher if plans for radical changes to the GCSE bear fruit, the head of Britain's biggest qualifications board has warned.
School halls will be virtually constantly in service as youngsters sit for modular assessments in January and June of Years 10 and 11, many of which they will then resit.
Exam boards, already struggling to keep up with a huge increase in assessment under the Curriculum 2000 reforms, will be forced to put up entry fees if "unitisation" of the GCSE goes ahead.
And the problems facing schools could dwarf those experienced following Curriculum 2000.
The warning comes from Mike Cresswell, director general of the Assessment and Qualifications Alliance. It coincides with a call from Ken Boston, England's exams regulator, for GCSE to become an entirely modular qualification by 2010.
Pupils would be able to build their own qualification from a series of increasingly challenging units, mixing academic and vocational modules, Dr Boston has said.
The move aims to combat snobbery towards vocational courses and is part of a major overhaul that will eventually break all qualifications down into units, offering youngsters more choice.
Some GCSEs are already modular, but they are still the minority, and are not yet offered on a "mix and match" basis with other subjects. Dr Cresswell told The TES that, if the qualification were changed in this way, more emphasis would be placed on pupils' results in individual modules.
As a result, lengths of papers would increase. Pupils would have four chances to sit papers in years 10 and 11, and would take advantage of opportunities to resit. He said: "Unitising the GCSE would unquestionably increase the assessment burden, on students to some extent, on schools very much, and on awarding bodies. The consequences of that would be very difficult to manage."
Dr Cresswell added that giving pupils true choice over which module to take and when would create huge difficulties for schools, which might have to offer teaching in small groups.
He said this did not mean the idea should be rejected. But the Qualifications and Curriculum Authority and the Government needed to "engage with" the implications of their plans. There was little evidence that this thinking was going on, he said.
Ministers have pledged to cut the number of exams in schools and the comments from Dr Cresswell, one of the country's leading assessment experts, will be a major concern.
A QCA spokesman said that unitisation was only one of a "number of options" being considered under a transition to a diploma system, which may be introduced in English schools by 2014.
He said: "No decisions have been taken about the timing of changes to current qualifications and any changes should reduce the overall assessment burden."