The deputy headmaster of a prestigious Melbourne private school who was sacked for cutting a student's hair has been offered his job back after a review found his dismissal was not justified.

Rohan Brown was fired from Trinity Grammar in early March for "contravening disciplinary procedures" when he cut the boy's hair before a school photo.

The decision was made by the school council.

Students held mass protests against the decision, who called for the long-term staffer nicknamed "Browny" to be reinstated.

In one instance, a truck mounted with LED screens with messages calling for the headmaster and the council to resign circled the school at pick-up time.

It also exposed a deepening rift over the direction of the all-boys school in Melbourne's eastern suburbs.

A week later headmaster Dr Michael Davies announced the school would hold an independent review into Mr Brown's sacking.

A truck with a billboard criticising headmaster Michael Davies was driven outside the school. ( ABC News )

The school on Wednesday announced the review found it "was not justified" and the teacher should be reinstated as deputy headmaster next Monday.

"While Mr Brown breached the school's code of conduct, and this may have constituted serious misconduct justifying dismissal, the headmaster Dr Michael Davies, who had the right to dismiss, had chosen weeks earlier not to end Mr Brown's contract," it found.

"School council, who dismissed Mr Brown following a code of conduct hearing, did not actually have the requisite authority to do so."

The ABC has contacted Mr Brown for comment.

Thomas Hudson, who was once part of the Old Trinity Grammarians Association believed he would accept the offer to return to work.

"From what I've heard he was in tears when he heard the news, he was with his wife and family and he is so excited to be returning for his 31st year at the school," he said.

Council apologises to school community

The review was carried out by former Federal Court judge Raymond Finklestein QC and barrister Renee Enbom, who represented Rebel Wilson in the Hollywood star's defamation case against Bauer Media.

The chairman of the school council, Robert Utter, said the council accepted the findings and apologised to the deputy headmaster.

Rohan Brown was sacked from Trinity Grammar on March 8. ( Supplied: Trinity Grammar )

"We would also like to extend sincere apologies to the wider Trinity community, with the original decision creating concern for many," he said in a statement.

"The attention Trinity Grammar has attracted in recent weeks has been regrettable and we hope our school community can come together and move forward with care and respect."

Among the five recommendations made by Mr Finklestein QC and Ms Enbom was that if Mr Brown wished to return to the school, the headmaster should advise him that "he should never in any circumstances cut a student's hair".

Mr Brown should also be told how the school's personal appearance policy should be enforced.