The Scottish Qualifications Authority will run two parallel sets of exams for the first two years of the new Nationals 4 and 5 to cater for pupils who are still following the current Intermediate 1 and 2 and Highers courses when the new qualifications are introduced in 2013.
The "dual running" exercise will require the exams body to produce two separate sets of exam papers and employ two separate sets of markers.
The SQA was unable to quantify the exact cost of "dual running" when asked by The TESS, but it is expected to be significant.
Karen McCallum, SQA director of operations, said: "We are working with the Scottish Government to ensure that the necessary resources are in place to support, develop and implement arrangements for qualifications, including dual running as a key part of Curriculum for Excellence."
The final certification of Standard grade will be in August 2013, and that of Intermediate 1 and 2 in August 2015
Ms McCallum added: "In practice, this means that the current P7 cohort will experience the new curriculum in the first three years of secondary school and will progress to newrevised qualifications in their S4-6 schooling. The current S1 cohorts will experience the existing curriculum and will still be able to progress to current national qualifications.
"The primary aim of dual running is, by accommodating the needs of different candidate cohorts, to provide a smooth transition between the different qualification systems. It is also important to ensure that no risks are taken with young people's education, especially in providing access and progression to current qualifications in S5-6 for those who have undergone the current curriculum in their S1-4 schooling."
Ken Cunningham, general secretary of School Leaders Scotland, said "dual running" had also been used as a safety-net when Standard grades were introduced.
"It is to capture people who have slipped through the net and make sure you catch the last of those doing the previous curriculum," he said.