Brighton Secondary College principal Richard Minack has been giving evidence before a trial brought by five former students, who allege they suffered years of discrimination and bullying at the school.

The students are suing the school, Mr Minack, teachers and the state of Victoria, claiming they failed to protect them under the Racial Discrimination Act and the UN Convention on the Rights of the Child.

The respondents have denied all allegations brought against them.

Mr Minack was on Tuesday questioned about a rise in anti-Semitism at the school after he gave speeches to assembly about his father, who fought for Germany in World War II.

He delivered the speeches to combat anti-Semitism and racism at the school, after parents approached him and urged him to do something, the Federal Court heard.

But a couple of days after one speech a student was caught playing tic-tac-toe at the school, using nine swastikas.

Mr Minack said he was "unaware" of any punishment given to the student, who two years earlier had sent a video to a Jewish student of Adolf Hitler doing a Nazi salute.

While he admitted the tic-tac-toe conduct was "undesirable", he said it was not intended to cause harm to any specific students.

"If this is not occurring in front of a Jewish person, doesn't that show a normalised culture of anti-Semitism at the school?" the students' barrister Adam Butt asked.

"I'm not sure, we're talking about an individual's actions," Mr Minack replied.

Asked if the speeches were ineffective since anti-Semitism continued afterwards, he said: "There's a percentage of students who won't listen or respond to anything you say."

He was pressed on a number of anti-Semitic incidents where there was no punishment or investigation, including a teacher who told a Jewish student to remove his yarmulke.

Mr Minack admitted there should have been an investigation into this.

"I would like to know the substance of this allegation and what was done," he said.

He said students should have been disciplined for saying "Heil Hitler" to other students.

"We should have considered more serious sanctions, including suspension."

Earlier, he said he regretted not apologising to Liam Arnold-Levy, who left the school in 2015 after suffering anti-Semitic bullying, including being held at knifepoint by students.

After leaving, Mr Arnold-Levy requested a meeting with Mr Minack to gain closure from his experiences.

"I certainly regret not apologising for what he felt, I regret not expressing that to him in that meeting," Mr Minack said.

The trial before Justice Debra Mortimer continues.

Australian Associated Press