cool kids
It appears that while so-called cool teens’ behaviour might have been linked to early popularity, over time, these teens needed more and more extreme behaviours to try to appear cool, at least to a sub-group of other teens. These previously cool teens appeared less competent – socially and otherwise – than their less cool peers by the time they reaches young adulthood. Professor Joseph Allen
Where to begin?
The "wiggle" words: appear, so-called.
Vague wording: young adulthood.
This "sub-group of other teens" is not defined.
These two sentences convey no information.
We conclude that whatever Professor Allen is attempting to relate, it is not applicable to the High Schoolers that we know.
G.D.O.