An elite private school in Melbourne is in disarray after the decision to sack a teacher for giving a student a haircut prompted legal threats, resignations and an outbreak of student protests.

Deputy headmaster Rohan Brown’s sacking from the prestigious Trinity Grammar school last week has ignited a wave of outrage amongst the school community, and has now led to the resignations of three senior school officials.

The controversy began when Brown gave a student a haircut before a school picture because it did not meet the school’s grooming guidelines.

He was subsequently sacked for allegedly “contravening disciplinary procedures”. In a statement the school’s headmaster Michael Davies said the school “takes seriously its duty of care to students, staff and the wider community”.

The decision set off a wave of recriminations, as students staged protests and school council members resigned in the face of legal threats to remove them.

This week some students wore “smart casual” clothes and untucked their shirts. During one protest they chanted for “Brownie” to be re­instated as they marched on the school’s oval.

Brown had been a teacher at Trinity for three decades, and outrage at the dismissal of the beloved teacher has reportedly spiralled into a deeper dissatisfaction with a perceived shift in the school’s culture towards a more results-based focus.

This week, 50 former captains and vice captains at the school from 2001 to 2017 signed an open letter to the principal and council chair raising concerns about “the change in culture and direction of the school”.

“In recent years, the school’s executive leadership has made clear its intention to change the school’s vision and direction,” the letter stated.

“This has seen a dramatic shift from Trinity’s position as a non-selective, not-elite school, dedicated to holistic personal development, to an institution focused on ‘exceptional’ performance defined by ATAR excellence, growth and profit.”

At a public meeting at the Hawthorn Town Hall on Tuesday the school community passed a no-confidence motion against Davies, and the Old Trinity Grammarians association has threatened legal action against Trinity if the entire council does not resign by Friday afternoon, reinstate Brown and demote the principal to interim headmaster with restricted powers.

The Australian reported that a student vice-captain told a school meeting that some boys would protest by not taking instructions on their presentation at school until Brown returned. “Until Mr Brown is back no one will tell us what to wear,” he reportedly said. “Until he is back to tell us to do so, nobody else can, and nobody else will.”

In such a febrile atmosphere the centre could not hold, and on Wednesday night three members of the school’s governing body, including council chair Rod Lyle and deputy chair David Waldren, resigned from their positions while still defending the decision to fire Brown.

“This behaviour was, in the unanimous view of the council, unacceptable and incompatible with the values of Trinity Grammar and with contemporary community standards,” they said in a joint statement.

“While we acknowledge the commitment and passion of those in the school community who object to the council’s decision, we are confident that we and the council will be vindicated in the action we took.”

The school council’s new chairman Robert Utter called for calm following the resignations and stood by the principal.

“It is time for Trinity to instil a renewed sense of calm and respect with and for each other,” he said.