Grades do matter in HS.
Source: Acceptance into a top university.
Grades are one part of the equation which includes many factors. All else being equal, better grades will put you above another candidate. Students with good grades were present regardless of their actual “intelligence”. This was because they put value in schooling and were successful due to that.
Grades still matter in college.
Source: Trying to get into competitive post-grad. programs.
See above - it’s the same shit.
The idea that one’s youth is wasted by studying (or learning or going to school) is generally an idea held by those who were unsuccessful in their own schooling or wildly successful out of schooling (the silicon valley college dropouts for example). While plenty of people do not need schooling to be successful in life. evidence still supports that one’s engagement in school and learning will lead to better outcomes. Grades are one (but not the only) metric of this.