I think this is being a little selective for a side that couldn't pack a scrum & didn't win a game.
Uni aside, most clubs had a couple of players who played 2nds at school.
A number of boys blossom late into very good footballers. They often train harder & want it more!
Uni's Prop all year in prem colts played mainly 3rds at nudgee.
The year before the 5/8 was from the NT and had only played 3 or 4 games of 15's a hand full of 7's games before playing at uni. He had never even heard of a pattern.
3 of the best players that year also came from Alstonville, mountain creek and Narrabri state high's.
Probably sounds strange coming from a uni bloke but far too much emphasis at colts level is placed on what kids did at which school and for what team. A lot of growing up happens from 17 to 19. Especially for those who haven't been blessed with good coaching/facilities/competition in the past.