Ofsted has said it wants hundreds more heads to become part-time inspectors as it looks to build bridges with schools and colleges.
The watchdog is demanding that a third of school inspectors - and half of those who assess FE colleges - should be serving practitioners.
Currently, a quarter of inspectors are principals or senior school staff, but at least 200 more senior school leaders must be recruited by the independent service providers (ISPs), the private inspection firms used by Ofsted, in order to meet the ambitious target by 2014. Currently about 700 inspectors work in a school or college.
The ISPs believe the move will "demystify" the inspection process and improve their relationship with schools.
The plans have received a mixed response from teaching unions, with NASUWT general secretary Chris Keates arguing that "serious issues" need to be sorted out.
She said: "How do they get paid? And what about issues in their own school - is it appropriate for them to be appointed to this?
"What will build a stronger relationship is where schools think they are being treated fairly, and that the process is open and transparent. If (Ofsted's managers) want to improve their relationship with schools, why don't they get good, practising teachers involved?
"Headteachers don't necessarily have recent experience in the classroom, and many have become divorced from it."
Russell Hobby, general secretary of heads' union the NAHT, welcomed the move, but said the recruitment drive did not go far enough. "I would say it's vital that more inspectors have current, credible school leadership experience," he said. "I'm pleased that Ofsted is responding to feedback and increasing numbers although one-third is not enough unfortunately."
Representatives from the three ISPs: Serco, CfBT Education Trust and Tribal Group - which provide 87 per cent of the 3,100 inspectors used by Ofsted - attended a hearing of the Commons education select committee looking at Ofsted's role and performance in January.