William Brennan carried on a family tradition when he graduated from the Army Recruit Training School Kapooka at the weekend, becoming the third member of his family to do so.

He followed in the footsteps of his older sisters, with one going on to become an Army reservist and the other a dental hygenist and Corporal based at Townsville.

Even his brother-in-law has been in the army for 12 years.

Mr Brennan, 18, and the fifth of six children, will now undergo specialist transport training before joining his unit.

The former All Saints College, St Peter’s Campus student worked in entry-level jobs at IGA, Hungry Jack's and Woolworths before enlisting with the army at the encouragement of his father, George.

The 12-week course at Kapooka proved to be a gruelling experience based on discipline and physical fitness.

"There's a lot of fitness, a lot of drill and a lot of equipment maintenance," Mr Brennan said.

"It can range from all-day marches to tiny detail like polishing brass.

"There's also a lot of classroom study – lessons on radios, weapons, night vision – all the cool stuff."

But it's fitness that is the biggest challenge.

"Our fitness is always being tested and it's always getting harder," he said.

"We started off with 25 push-ups and 65 sit-ups, plus a 2.4km run in under 12 minutes.

"Then it goes up to 35 push-ups, 75 sit-ups and doing the run in under 11 minutes 18 seconds.

"We also end up carrying 15kg packs.

"I'm enjoying the competitive fitness side, but I also feel I've matured heaps."

Proud father George conceded his son's decision to join the army came with "a bit of influence from me".

It was the third graduation ceremony the family has attended at Kapooka, but the proud dad and former policeman said he hadn't gotten sick of them.

"I really think the defence force offers better opportunities," he told the Mercury.

"You come out of it with qualifications that carry into the civilian world."

Mr Brennan said although his time in the army was short, the experience had already changed him.

"My parents said I would come in a boy and leave a man," he said.

"I used to be a bit of a surfie, wandering around with my shirt hanging out. Now I'm much more presentable and have a better sense of what's good and what's bad.

"My mum and dad were right."