Yup, mentioned frequently, and a great starting point for thinking creatively about schools. I wouldn’t take membership in CTCL as an automatic badge of quality for a given kid, because they occupy QUITE a range of selectivity and quality, but they’re worth investigating, and if there’s a session near you, it’s well worth attending, as much for the perspectives offered as for the schools themselves.
My kid visited four CTCL schools, has applied with great enthusiasm to one of them (another runner-up didn’t make the final cut and two fell off quickly), and has applied to several other more far-flung ones sight unseen after learning more at their info session, along with some further follow-up.