But he has maintained his sense of humour throughout his journey, and has been buoyed by the support he has received from friends, family and his school community.

The Tomaree High School teacher, who is currently on sick leave, said he has been blown away by the support staff and students have shown him since a brain tumour was found in October 2016.

This week the school showed further support for Mr Gallagher and an organisation that has helped him during the past eight months – the Mark Hughes Foundation.

On Thursday, staff and students donned beanies for a fund-raising day.

"I have to thank the school for what they've done," Mr Gallagher said.

"I take my hat off to the staff and students for doing this. It's a really nice thing to do."

Mark Hughes, well-known for his days as a Newcastle Knights player, visited Tomaree High School during the beanies for brain cancer fund-raiser on Thursday.

During a brief assembly, Mr Hughes spoke to students about his foundation, which he began after he was diagnosed with brain cancer in 2013.

He thanked the school for supporting the foundation, and Mr Gallagher.

Beth Adam, a teacher at Tomaree High School, and the student forum organised the day.

Ms Adam said that day was in support of Mr Gallagher as well as many other students and teachers who have been personally touched by cancer in their families.

"It is great to see the face of the foundation getting out to the high school and chatting with the kids and staff," she said.

Casey Ballard, 15, said the student forum had been planning Thursday's beanies for brain cancer day for some weeks.

"We really want to raise money for the Mark Hughes Foundation because what they do is important to us, too," she said.

Many students, including the school's year 11 and 12 hospitality classes, donated bakes treats to be sold on the day.

The barbecue was busy throughout lunch.

School principal Sue Xenos said it was "great" that the students had embraced the beanies for brain cancer fund-raising concept.

Mr Gallagher, who has been a wood and metal teacher at the school for 15 years, also attended the fund-raiser on Thursday.

A scan found a tumour on Mr Gallagher's brain in October 2016.

"It all happened really quickly after that," he said.

Mr Gallagher was sent to John Hunter Hospital and a week later was operated on, with neurosurgeons removing the tumour.

He was diagnosed with grade four brain cancer, "the worst kind", and was given a dire prognosis.

It was only last week that he finished chemotherapy, and on Wednesday had his latest scan.

For now, it is a wait and see scenario.

Mr Gallagher, who is just 58 years old, has regular blood tests, some of which have been sent to universities to study, and will have a brain scan every three months from now on.

"My specialists, I have three, are stunned with how well I'm going," Mr Gallagher said.

The Mark Hughes Foundation has supported Mr Gallagher since he had the operation to remove the tumour last year.

He thanked the foundation for their support, and Mr Hughes for attending the school on Thursday.