"As a result, the school council was of the view that Mr Brown’s leadership position at the school was no longer tenable," Mr Lyle said in the letter.

A video obtained by The Age shows Mr Brown, who is in charge of discipline, snipping a lock of hair from student's head while boys giggle in the playground.

School rules state that a student's hair must be off the collar.

The decision has shaken the school community, with parents threatening to withhold fees until Mr Brown is reinstated. More than 500 people have already signed an online petition to "Bring Brownie back".

An emotional Mr Brown, who worked at the school for more than 30 years, told The Age that he loved Trinity and was saddened by what had unfolded.

"I would like to go back," he said. "It’s a good school and this is tearing me apart. I can't comment further."

Many former students believe Mr Brown's sacking is political.

Tensions have been brewing since November, when Old Trinity Grammarians' Association president David Baumgartner sent a scathing letter to the council chair and headmaster, accusing the prestigious private school of becoming too preoccupied with high ATARS, fundraising and building projects.

This was a school which produced well-rounded men who had an interest in the wider community not just their pay packets and status. The school is being destroyed.

Former Trinity Grammar student

Mr Baumgartner, who has served on the association for 34 years, wrote in the letter that there was a "resurgent undercurrent of frustration and anger" among the school community.

"There is too much inward focus on things like buildings, fundraising, marketing, ATAR excellence, Cambridge schooling program, etc," he wrote.

One former student said Mr Brown stood in the way of the headmaster Dr Michael Davies' vision for the school.

“Rohan represented the old school's values, caring for the community and the moulding of young gentleman,” the student said.

“This was a school which produced well-rounded men who had an interest in the wider community not just their pay packets and status. The school is being destroyed.”

Tim Sharp, who sits on the Old Trinity Grammarians committee and is the organisation's former president, did not want to comment on the incident other than to say he had absolute respect for Mr Brown.

"He is the backbone of what we want the school to be," he said.

This week Mr Sharp excitedly phoned the school to inquire about enrolling his newborn son.

But he said he received a lukewarm response.

"There was no congratulations or thanks for considering Trinity," he said. "It was print out the forms and 'No we don't care if you are an Old Boy."

He raised concerns about this interaction with Mr Brown, who personally delivered the enrolment forms to his house at 7pm on Wednesday.

"That's the sort of guy that he is," he said.

Former teachers who contacted The Age said there had been an exodus of staff since Dr Davies took over the role of principal from Rick Tudor in 2014.

One teacher estimates that 152 teaching and support staff have left the school in the past four years.

Old boys have set up a Facebook group for concerned members of the school community and are calling for Mr Brown to be reinstated.

"As a school community it is time we take a firm stand to protect the legacy of the school and its proud 114 years of history before Dr Davies succeeds in destroying all that is right and good with our culture," they wrote.

But a current student at the school, who did not want to be named, said it had improved under Dr Davies' leadership.

"He has hired some of the most fantastic teachers, the renovations that are planned are incredible and his door is always open," he said.

Trinity Grammar was due to host a meeting for concerned parents on Friday evening.

It has been contacted for comment.