Guys, I think I've cracked the code. I know the in-universe process for who gets selected for RSA versus NRC! And it's not jerks/villains and goody two shoes/heroes.
RSA gets all the ones actually capable of self-reflection and healthy communication. And NRC takes all those who would quite literally rather DIE than so much as admit they have a problem, let alone ask for help.
No, genuinely, I'm not joking. Think about it, it makes sense. Even those that don't really fit the "stereotypical" NRC student image fit this criteria. Kalim has a problem with admitting he has problems, Silver preferred to get eaten by dream monsters than live with his revealed blood lineage, Ortho is a robot, Jack is a tsundere. I could go on and on.
And while we haven't seen too many RSA students yet, I think it's already obvious they're better way at this than NRC. Forget the princess glow - this is how they've really been winning over and over again! The secret is that their school environment is overall far less toxic!