Are you really going to get maturity or just superficial signs of maturity from immature kids? I think kids that more boldly explore social interactions (ie. naughty) at a young age may end up more mature as adults. Someone who's polite and well-behaved may doing that because they're too emotionally immature to know how to do anything more risky and are just performing "professional behavior" which is a kind of lowest-common-denominator for getting along with others.
In practice, I feel you're right. It will simply devolve into a superficial display of maturity being used as the right metric while real, deeper signals are buried or ignored in the face of superficial counter-signal.
Worked as something of a TA in several high school computer courses (MS Business Applications, Programming (Basic), Programming (Java)) with many students of varying levels and competencies. Was quite a fond memory in quite a lot of ways. Schools should encourage more of that sort of thing and less batshit test prep. Unfortunately, true well-rounded human beings don't solicit eyeballs and award shows and budget dollars.
