It is essentially how it worked for Spartan 2 program, except they had multiple candidates, Halsey checked all of them out and their skills and what not at a young age, chose I think it was 150 or so maybe it was 300, started the training with the pelican, cut those that wouldn't jump outta it, cut those that didn't do the daily activities, started the augmentations and blah blah blah if you read the books you know the rest xD
But soon after kidnapping them Halsey replaced them with clones...