The Assembly government is poised to intervene directly with schools and local authorities deemed too slow in overhauling post-16 education.
Education minister Leighton Andrews has said there is a limit to his patience and the next government may need to be more "persuasive or directive" in ensuring that the post-16 so called "transformation agenda" is delivered.
All 22 local authorities are restructuring their post-16 provision in a bid to save money, reduce competition and raise standards.
The minister said intervention and financial penalties may be necessary if providers do not act quickly to improve standards, leading one head to accuse Mr Andrews of "bully boy tactics".
Responding to questions from the Assembly's enterprise and learning committee, Mr Andrews said: "There's certainly a limit to my patience. We need to move faster in some areas of education and this is one of them.
"Local authorities have brought forward proposals, but not all have met with our approval."
Mr Andrews said the FE sector has been the most "dynamic" in adapting to the challenge, and was providing a leadership role.
Although he did not criticise schools directly in his evidence, a supporting document from the government said some 11-18 schools had a "vested self-interest" and an "unwarranted perception" that FEIs offered a lower standard of provision and pastoral care, which was a "major impediment" to transformation.
It also admitted that many schools with sixth forms would "struggle" with a 1.5 per cent reduction in funding in 201112, but Mr Andrews said that would be "no excuse for staving off change".
Neil Foden, head of Ysgol Friars in Bangor, Gwynedd, said: "The last thing we want is more persuasion and direction; the whole sector is a mess. Heads feel the FE sector is favoured over schools. As far as schools are concerned, the minister doesn't know what he's talking about."
Gwynedd has taken a collaborative approach to its post-16 transformation, but a government report said it has made slow progress.
Mr Foden added: "We have successfully implemented the transformation agenda. We don't need these bully-boy tactics."
NAHT Cymru director Anna Brychan said schools were being unfairly criticised. "Members have become frustrated dealing with rounds and rounds of planning for projects, only to find that local authorities simply can't achieve the political consensus to go forward," she said.
Dr Chris Llewelyn, director of lifelong learning for the Welsh Local Government Association, said: "Authorities recognise that these are difficult times, but all stakeholders have to collaborate to overcome these challenges."
Original headline: Improve or I'll intervene: Andrews' post-16 ultimatum