Of those interviewed, only a third said were likely to apply for promotion in the next five years. Extra responsibilities and administrative burdens were a major factor.
The findings show that becoming a head is not automatically included in senior teachers' career plans, a seminar organised by the Scottish Association for Educational Management and Administration was told.
Research by Janet Draper, head of social science and social work at Moray House, and Paquita McMichael, her predecessor, found that deputes between the ages of 31 and 40 were keenest on taking the top job. In contrast, 80 per cent of those over the age of 50 were not considering applications. None was tempted by a rise in salary.
A surprising 80 per cent admitted they would not apply for a head's job in a small school because of the teaching commitment. Delegates said this would not have been the position 10 years ago.
A profile of potential heads shows deputes had to have enough time in their existing post to gain experience, have fewer family constraints and be under 50.
Many deputes believed they shared a head's duties in areas such as staff development, the curriculum, management of resources, discipline and relationships with staff. But they noticed a difference in duties over responsibility for buildings, finance, school boards and appraisal.
Deputes said previous management experience and experience of managing and developing the curriculum were the key to promotion. Ability to handle finance was rated less highly.
Sheena Liddell, head of Winchburgh primary, West Lothian, who was seconded for two years to a Lothian management project, said: "You are a manager of a small business. I would have thought devolved school management and financial skills would have rated more highly." Her head was buried in spreadsheets every day.
Mrs Liddell said there were "significant differences" between the role of a head and a depute. "The head inspires and gives leadership to the team, " she contended.
Becoming a head was about teamwork. Deputes had to go into the job "with their eyes open".
Andrew Bruce, head of Craigmount High, Edinburgh, who was also seconded to a management project, concurred with the survey findings. A similar percentage of deputes in secondary were unlikely ever to apply to become a head.
Mr Bruce suggested that deputes saw primary headships in a traditional light but the job had changed.