To mark the Australian Defence Force's 125th anniversary, students at South Sydney High School have spent recent months sketching, chatting and connecting with local war veterans for a national portrait competition.

The school's High Potential and Gifted Education (HPGE) Creative and Performing Arts students were invited to take part in the ADF's Our Australian Soldier Art Prize, capturing their personal interpretations of what an Australian soldier represents.

Eleven veterans and current service personnel from the Botany and Maroubra RSL Club Sub-Branches visited the school to sit for live portrait sessions, sharing their stories of service while students worked.

Principal, Janice Neilsen, said the project had strengthened an already valued partnership with the local RSL community.

"We've always had a relationship with the RSL, but this deepens it, both for the students and the veterans and the community, so it's great to be able to have greater connection with them," Ms Neilsen said.

Ms Neilsen said the idea began as a way to extend the school's HPGE artists, with students nominated by their teachers before the RSL clubs were approached.

"They were really excited to participate, and they offered us live volunteers to come and sit with their portraits," she said.

The artworks have now been submitted to the ADF, with the outcome due later this year. Successful entries will be exhibited at the Australian War Memorial.

Many students have chosen to gift their finished portraits to the veterans who sat for them, alongside a commemorative book documenting the day in photographs and finished works.

Head Teacher Creative and Performing Arts, Kate Mulheron, said staff hoped to make the project an annual fixture.

"It's nice, the bringing together of the generations," Ms Mulheron said. "Many of our students don't have grandparents or elder people in their lives, so I think it was really a very enriching experience for them."

The project carries a bittersweet note.

One of the veterans involved, 101-year-old George Johnston, passed away before the exhibition could take place. His son Alan and granddaughter Nicola, both South Sydney High School alumni, attended the exhibition in his place, a fitting link given three generations of the Johnston family have passed through the school's gates.

Year 9 student Natalie Helikarova, who drew George's portrait, said the experience had stayed with her.

"It was a really nice experience to speak with George. We talked about his time in the war and I did sketches. He was such a lovely man," Natalie said.