Not 100% sure what you're getting at Metal. I tend to think of private academies as youth finishing schools and if a player feels he wants to do that, fine - hence, Rufer, Tuiloma spent some time doing just that. All feds run FTC/NTC 'academies' up to 16; not all players are in that programme; some may or may not be in private academies.
As to Chch at 2013 U17 level; one Cantab made 2013 NZ secondary schools team to UK; a couple went to this year's Milk Cup with the Otago team; Burnley academy are not getting best quality players (only out of town kids north and south of Chch) and APFA at 2013 U17 level have only 2 Chch lads - one who missed getting a trial and one who never was going to get one; the rest were/are in club/FTC/NTC. My point is that on a pro rata population basis - on average - you would expect 4-6 Sth Island/Chch kids in any given national squad. This year was one and last world cup was 2 (I think). Just seems a bit under-represented and doesn't seem to happen with the girls.