It emerged later that the Scottish Secretary already has powers to impose the qualification by regulation, although there is little likelihood of him doing so.
Concern was raised at a conference in Edinburgh, one of three consultative meetings to shape the qualification, that non-teachers with management training may be hired to run schools. John Kelly, past president of the National Association of Schoolmasters Union of Women Teachers, suggested this could be the result of linking the qualification to general management awards available through the SVQ framework.
But Scott Carmichael, a principal officer in the Scottish Office Education and Industry Department, said it was unlikely non-teachers would be brought in to run schools. Candidates would have to be registered with the General Teaching Council before being accepted for the Scottish Qualification for Headship (SQH).
School leaders were also assured that the qualification would be heavily based on practice. "The key thing we were told during the consultation period was that we don't want people who know it all but can't do it," Jenny Reeves of the SQH development unit said.
The new qualification is being strongly backed by the Inspectorate whose Standards and Quality report pointed to weak leadership in 20 per cent of primary and secondary schools, and unsatisfactory leadership in 5 per cent of schools.
Mr Donaldson warned, however, that "there is no one way to lead a school". Heads had to deal with difficult and complex issues - meeting statutory requirements, reconciling differing views about the purpose of the school and the nature of education, standing up to external scrutiny, balancing professional autonomy with the needs of the school, and dealing with children.
Viv Casteel of the SQH development unit said the national standard for headship would be based on the recognition that the job was "an art form not a science which could be divided up into neat bits". It had to take account of interpersonal and intellectual abilities (courage and wisdom are two of the standard's cited requirements).
While there appeared to be a general welcome for the way the qualification is being developed, the programme has still to clear up how aspiring school managers are to be selected, assessed and paid for.
Christine Pollock, depute director of education in North Lanarkshire, said: "It is important to be fair to our workforce so everybody has access to the qualification, and it is also important that it does not miss out on those who have learned on the job in terms of acknowledging their previous experience. "
Staff development was also crucial, Ms Pollock said, and resources must not be diverted from existing budgets. "Nothing would be worse for staff morale. "
The Scottish Office is unable to put figures on the costs of obtaining the qualification, for authorities, schools or individuals, until May or June after the Treasury's public spending review is complete.
The development unit is now set to produce criteria for would-be candidates, guidelines to help them assess their potential, materials for staff development, and a system to measure candidates' achievements accurately and fairly.
Initially the SQH will be aimed at those on the point of applying for headships. Experienced secondary deputes could be ready in as little as six months but senior primary staff with little management background would take longer. The qualification could eventually reach down to principal teacher level.