An industrial dispute over a secondary's conversion to academy status came to a head this week when the leader of teaching union the NASUWT was banned from the premises.
Chris Keates has written to education secretary Michael Gove to complain after the head of John Port School in Derbyshire denied her permission to address members on school property, just days after it became an academy.
Ms Keates insists she has never been refused entry to a school before and makes a point of meeting with members in schools with intense or long-running disputes.
Teachers at John Port have walked out on seven separate occasions. Ms Keates said other schools around the country where the NASUWT was challenging academy conversions had allowed her to visit.
In her letter to Mr Gove, she said it was "difficult to conceive" of any reason that would "prompt or justify such a discourteous and unusual response".
However, it is unlikely that Mr Gove will have sympathy for Ms Keates, as he recently told the union's local rep to "tell his (striking) union colleagues to get back to work and do the job they're paid for".
Wendy Sharp, head of the 2,100-pupil school, told The TES that to allow the leader of the union that had caused extensive disruption to speak at the school would be "wholly inappropriate" and could enrage parents whose children's education had suffered as a result of the strikes. "It's an unreasonable request," she said.
She added that she thought the NASUWT was using the dispute at the school as a way of highlighting its political opposition to the Government's overall academies policy.
"We have had seven days of strike action and two months of refusal to work to contract," she said. "This, to the best of our knowledge, is more action than at the other schools.
"They should be taking their case to the Department of Education. Why should the students be the victims of their political view?"
She stressed that the school had never refused to work with unions, meeting them six times a year, and that the union would be recognised under the academy arrangements.
But Chris Keates lashed out against the attitude of the school's management to her visit, which will now be held in a local hotel.
Ms Keates, who has written to the head claiming the snub sent out "a deeply negative message" about the schools' attitude to unions, said: "It is not the headteachers' school, it's the workplace where the people are. The fact that we have a different opinion and are exploring a possible challenge isn't justification for banning somebody from the premises."
Education secretary Michael Gove launched an unexpected attack on the NASUWT this week for criticising his new policies on behaviour.
In a statement, Chris Keates said a raft of announcements designed to improve discipline in schools were "more about securing populist public support than backing teachers".
But at a press conference, Michael Gove told reporters: "I'm worried the NASUWT is not serving the interests of its members as it should.
"Those in charge are busy upbraiding ministers for not doing enough, but here we are seeking to support teachers."