Cooper, in year 11, will turn out for Combined States at this week's national championship at Sydney's Riverview College, winning a shock call-up to the composite side after starring for the Independent Schools Association's second XV at the NSW Schools trials last month.

Combined States encompasses identified players from the states which don't field a stand-alone side and then includes the, for lack of a better term, best-of-the-rest from NSW, Queensland, ACT and Victoria who miss out on selection in their state sides.

For the most part those players tend to be the young guns who, like Cooper, are eligible for at least one more year, giving them a chance to shine on the national stage and remain on their respective states' selectors' radars.

"I thought I'd be in the twos for Kinross so even getting picked for ISA for massive," Cooper said.

"I thought I might be a shout for the thirds there but then I got picked in the firsts squad, and dropped down to seconds in the end. It opened my eyes a little bit, but it gave me a lot of confidence knowing I was on the radar, that sort of made me think 'I can do this'.

"We got put to the sword by a really strong [Combined Associated Schools] side at the NSW trials so I wasn't expecting anything to come of it, I was just happy with the experience.

"I thought ISA would be it and I'd have been happy with that, so getting the phone call for Combined States was a massive shock, it's pretty exciting."

Cooper and his Combined States side have been in a 'pretty full-on' camp since Saturday afternoon, in preparation their tournament-opening clash against Victoria on Tuesday afternoon.

He admitted he knows nothing about the southerners, he doesn't know much about his own teammates to be fair, but with this year's nationals adopting a knockout-style format he said he's hopeful his side can produce something special.

"There's no pressure on us, you know. We don't have the expectation on us that sides like NSW or Queensland have, we don't have any big shoes to fill which is good, we can just go out and play the game we love and have some fun," Cooper said, that devil-may-care attitude often pays dividends in tournament rugby too.

"Combined States get talked down sometimes but the message from the coaches is that we're not just here to fill a hole, we're here to play some good rugby because they want to see more of us and that's a real confidence boost too.

"One of the great things about this side I think is that we don't know each other. I've met guys from South Australia and the Northern Territory, there's a few Tassie boys too, and we're all getting along really well, we just want to play some footy together now."

As you'd expect his Combined States selection has given Cooper the chance to reassess his goals. The Australian Schoolboys Barbarians side will be picked from the nationals, which double as one facet of the selection process for the top tier national side that will tour New Zealand in September.

That's not Cooper's focus, he's shifted to his gaze to a NSW jersey next year.

"I guess if I play good rugby I'll give myself every chance to make [the Australian sides] but it's more about the experience, it could be a once-in-a-lifetime opportunity after all," he said.

"But the NSW trials with ISA, that gave me a lot of confidence and I've set myself a goal of getting picked for NSW II next year."

Cooper's Kinross skipper Will Smith is in that NSW II side this year, the prop's second state gig, the outfit is gunning to go one better than last year, they faced NSW I in the decider in 2018.

St Stanislaus' College Bathurst skipper Cam Trengove is in the NSW I side, he'll run from the bench behind incumbent Australian halfback Lachlan Albert.

The nationals kick off on Tuesday, with the day one winners progressing to the championship side of the draw, and continuing on with each victory. The finals will be held on Saturday.