Training and preparation that involved classroom teachers and not just principal teachers might have brought them on board earlier and avoided current difficulties, Mr Tuck told secondary heads in Crieff .
His frank admission accompanies frantic talks behind the scenes earlier this week to resolve the impasse in implementing Higher Still caused by the impending Educational Institute of Scotland boycott. It is believed ministers had Downing Street backing to take on the union.
It now seems certain the boycott will be suspended to allow a restructured Higher Still liaison group to work out local implementation details. The group will act as a court of appeal, deciding which local authority plans will proceed and at what pace. One insider said: "There is a remarkable new spirit and an absolutely genuine attempt to resolve this with everyone on board. "
In that new spirit, Mr Tuck, chief executive of the Scottish Qualifications Authority and a member of the liaison group set up by Helen Liddell, the Education Minister, to unravel the problems, admits implementation could have been handled better.
In effect he confirms the view expressed last summer by Brian Wilson, the previous Education Minister, about over-optimistic advice on the state of readiness.
"On reflection, perhaps we called it wrong," Mr Tuck said. "We made a mistake not giving teachers at classroom level extra in-service from year one. But decision-makers had to balance that against the problem of taking teachers out of the classroom and jeopardising current pupils."
Michael O'Neill, director of education in North Lanarkshire and a key local authority adviser, said "national reassurance and local flexibility" were vital in unlocking the jam. Critical comments in last week's TES Scotland by Ross Martin, the Convention of Local Authorities' education spokesman, were retracted as part of the peace deal.
The new accord, still to be ratified by the EIS executive, will extend liaison group membership but confine it to professionals. There will be no direct political input. The group meets again next Wednesday, and EIS members are expected to attend.