An independent headteacher with 20 years of classroom experience was not even considered for a headship at a Warwickshire comprehensive school because he does not have qualified teacher status.
The decision comes as the Government is pushing for non-teacher heads, particularly in academies.
John Price is principal of the 1,330-pupil Jerudong International School in Brunei. His CV notes 11 years' teaching experience at Winchester College, a leading independent school, but George Eliot Community School in Nuneaton did not consider him because he does not hold the right accreditation to teach at a state school.
Mr Price said he faces a "brick wall" when trying to find work in the state sector because he does not have qualified status - a training award introduced after he became a teacher. "I understand that you have to assess candidates, particularly if you are newly qualified, but there must be a better way of assessing someone when you have 20 years of experience," he said.
"I don't think there is any doubt that a head who has experience of teaching would do a better job than, say, the managing director of Shell.
"It seems a bit rich, especially when you hear the Government is having trouble filling many head's positions in the state sector."
Mr Price, who was educated in the state sector, said he did not believe that because a teacher spent their career working in independent schools they would "find it difficult to cope" in a comprehensive.
The Department for Children, Schools and Families told The TES that it "welcomes applicants from outside the maintained sector" and that it "wouldn't want to rule any good candidates out". It also said it remains committed to encouraging non-teachers to apply for headships.
A spokesperson said: "We want to make it possible for experienced leaders outside the schools sector to become headteachers. The accelerated leadership and development plan that the National College for School Leadership plans to launch early next year will provide a pathway for those outside the sector to work their way towards the national qualification for headship (NPQH)."
A Training and Development Agency for Schools spokesperson said: "The qualified teacher status assessment-based training option offers teachers the chance to demonstrate they meet the standards required to achieve QTS by submitting a portfolio of evidence of their abilities as a classroom teacher."