Trinity Grammar has plunged further into crisis after three members of its school council, including its chair, resigned in the wake of their controversial decision to sack a popular deputy principal.

Facing intense criticism over the council's handling of the incident, chair Rod Lyle and deputy chair David Waldren said in a statement that they could no longer continue because sections of the school community did not share their values.

"We maintain that we and the council acted with integrity and in the best interests of the school – its staff, parents and, above all, its students – in taking action over the recent behaviour of the school’s former deputy headmaster, Mr Rohan Brown," they said.

“This behaviour was, in the unanimous view of the council, unacceptable and incompatible with the values of Trinity Grammar and with contemporary community standards."