Apparently adolescence is getting longer with people not taking on an adult life to they get past 25 sometimes. Umpteen years in college, bad economy keeps you living with parents etc..
On the other hand, Star Trek regularly portrays 8 and 9 year old children studying calculus, programming, engineering, at levels which would be good for most 2nd or 3rd year undergrad students (approx age 20) for contemporary humans. In the Star Trek universe, human mental development would seem to be about twice as rapid.
I mean, you see occasional exceptional students even right now in the real world, but they are truly the exception, not the rule, whereas in Trek, they seem to be pretty much the "normal" kids.