Originally Posted by intparent
But the preparation for university should be academic.

You did ask about Ivy League Admissions in your original post. And whether you prefer it to be that way or not, purely academic preparation will not get you into any of the Ivies, probably even the "lesser Ivies", today.
A student whose ECs were an extension of his academic interests, for example scoring at the national level on the Math, Physics, Chemistry Olympiads, and/or doing scientific research, could be a strong applicant. You can get in as an academic star, but being a valedictorian with almost-perfect test scores does not make you a star, especially if you are deemed "privileged".