Alex Easton, the rector of Falkirk High, told a conference this week that, while no final decision had been taken in Scotland, heads in England will be required to hold a qualification by 2002.
Mr Easton, who is a member of the team developing the Scottish Qualification for Headship, said it would have the advantages of being work-based, allow previous experience to "fast track" towards the award, and ensure that aspiring heads were able to lay "more systematic and less arbitrary" career plans.
He added, however, that holders of the qualification would not be guaranteed headships. "It will become necessary but not sufficient and will complement existing appointment procedures," he said.
But there were unresolved issues, Mr Easton told the annual deputes' conference of the Headteachers' Association of Scotland in Battleby on Tuesday.
Who would accredit and award the SQH? How would it be delivered? Could fair access and selection be ensured? How would funding be apportioned between the authorities, schools and candidates themselves?
Mr Easton believed every education authority should be given a quota of SQH training places, so that each would get its fair share and did not piggy-back on training carried out by others.
It was also important to ensure that staff in small rural primaries had the same rights of access to the course as their colleagues in large city secondaries. But Mr Easton acknowledged that it would be easier for the latter to accumulate experience which would count towards the qualification.
The scheme envisages that previous experience could enable a candidate to fast track to the SQH within six months, while those unable to establish prior accreditation could take up to three years.
Mr Easton revealed that there was pressure, for candidates to pay for their own course. The argument was similar to the debate over tuition fee charges that, since the qualification would lead to higher paid jobs, the 'student' should make a contribution.
But this view was now being challenged by those who suggested that, since the SQH was a national initiative, the Scottish Office should fund it.
The inspectorate believes that the 20 per cent of secondary heads who are said to be under-performing are mostly deficient in their inter-personal relationships rather than in knowledge about the job.
"It's not just what you do, it's the way that you do it," Mr Easton very nearly said.