Here is the list
en.wikipedia.org
Not sure what the % is. I didn't have the time or attention span to run through it that forensically. But I would say 40-50% for sure have gone on to have at least respectable first grade RL careers.
Just a snapshot of the 2015 and 2016 teams, the age group that should now be prime time NRL age bracket, shows a pretty solid alumni. At least 17-18 out of the 34 listed are regular NRL first graders.
2015 Australian Schoolboys
Ryan Papenhuyzen, Tyronne Roberts-Davis, Curtis Scott, Reuben Garrick, Tre Williams, Nathan Cleary, Scott Drinkwater, Jye Challenor, Blayke Brailey, Jayden Butterfield, Cameron Murray, Adam Keighran, Reuben Cotter, David Fauid, Ray Stone, Bayley Faull, Daniel Vasquez.
2016 Australian Schoolboys
Nic Cotric, Mawene Hiroti, Zac Lomax, Tuimavave Afualo, Campbell Graham. Lachlan Lam, Sean O’Sullivan, Pasami Saulo, Blake Brailey, Thomas Mikaele, Brodie Jones, Josh Curran, Sean Keppie, Dean Blore, Reece Robson, Payne Haas, Michael Tupou