When Liam Birrer was helping fight the Crestwood Drive fire south of Port Macquarie at Lake Cathie on Tuesday he had somewhere else he should have been.

The 18-year-old student at Hastings Secondary College's Westport Campus was due to sit his Metal and Engineering exam at 2pm but instead he was with his Rural Fire Service colleagues.

He said it was not a tough decision to make to head to the fireground.

"It's not like I just ran out and didn't tell anyone, I called the school and let them know," he said.

"I was sitting there listening to the scanners and I just didn't want to sit around and do nothing while those guys were out there."

Liam Birrer is a volunteer firefighter with the Rural Fire Service. ( Supplied: Brittany Daly )

Mr Birrer has been a volunteer with the Sancrox-Thrumster brigade for the past two years.

He plans to make an illness and misadventure application to the NSW Education Standards Authority in the hopes of getting a good mark.

"I talked to the principal and he said I can put in a misadventure form and they'll just average out my marks for the year and give me that as my mark for the exam that I missed."

He has one more exam next week.

"I still have chemistry to go but I don't think I'll be ditching that one."

Principal 'very proud'

Ian Ross, the Principal of Hastings Secondary College's Westport Campus, said he's "very proud" of Liam's efforts. ( ABC News: Kerrin Thomas )

Principal Ian Ross said he was not surprised by Mr Birrer's actions.

"Knowing the boy and knowing his family, it's just a classic example of a lovely young man who's putting community and family in front of himself," he said.

"It's a really selfless act and he's to be congratulated for it."

Mr Ross said he expected the illness and misadventure application would be successful.

"A lot of people that I speak to have a negative view on young people, but then you hear stories like this and they go, 'That's fantastic, we weren't expecting those sort of outcomes,' and for me, as a school principal, I'm very, very proud of these students," he said.

"I don't know how to respond to those comments, it's nice to hear but I'm sure there's better people out there but I'll take that," Mr Birrer said.

Future plans

Mr Birrer hopes to head to university next year but also has another career goal in mind.

"I'd love to take up firefighting as a job but I don't know if I can do that straight out of school," he said.

"I'll definitely throw my hat in the ring every year for that but other than that I hope to go to university and do something with environmental sciences."

And he is encouraging others to join their local RFS.