CTC, Oxford and CAE place a lot of people with partner airlines, but this has absolutely nothing to do with "aptitude"
They all have set up a system that gives them significant tax benefits, and they also have a cashflow going into the airlines to get their students first in line. Students pays twice the market rate, school makes massive profit, airlines get bunch of people with a known baseline of skills jumping at the opportunity to work for peanuts. ATPL scores, first time passes, etc mean very little in this scenario. This come straight from the horse's mouth; The man who explained this to me, albeit a long time ago, used to work for one of these training providers. It's is at best unethical, but all fully legal.
I personally know people that did extremely well during their training, and simply don't get called. One of them actually passed the CTC aptitude test but decided against it due to the ridiculous course fees. And I know plenty of people that absolutely scraped by but went to a fancy school, and are now sitting in the RHS.
It's not about being good, it's about getting a chance/making your own luck. And sadly these big schools have cornered a big part of the labour market.