The Secondary Principals Association says it has been made aware of several disputes between principals and boards of trustees since the sacking of the head of Christchurch Girls' High School.
Principal Prue Taylor was dismissed this month but took her case to the Employment Relations Authority and won interim reinstatement last week.
Board of Trustees chairperson James Margaritis resigned from his role on Tuesday over the row though he remains on the board.
Mr Margaritis was one of the senior management group which sacked Mrs Taylor over what it said was her bullying behaviour towards some staff and a breakdown in her relationship with the board.
The principal's lawyer told the Employment Relations Authority hearing that the catalyst for Mrs Taylor's sacking appeared to be her suspension of Mr Margaritis' daughter, but the board disputes this.
Association president Patrick Walsh says six or seven principals have come forward since Mrs Taylor's case was made public.
He says the principals claim their relationship with trustees soured because of perceived injustices with the trustee's children or in some cases their friends' children.
Mr Walsh says examples given include a trustee's child being suspended, and in one case a child not being selected for a top netball team.
Board member defends sacking decision
A representative of the Christchurch Girls' High School board has rejected suggestions its sacking of principal Prue Taylor was a mistake.
The Employment Relations Authority said there was no justification for her dismissal.
Board member Tim Priddy told Radio New Zealand's Morning Report programme the sacking was not a sudden move.
"This was the culmination of a long period of if issues, of mediation, of a disciplinary process. For it to be suggested that this is some sort of kneejerk reaction is just quite outrageous."
Mr Priddy says the board is looking forward to presenting its case in more detail at a substantive hearing at the Employment Relations Authority in February.