The optimal amount of stress about that stuff is not zero, and most teenagers are going to be desperately biased towards "none of this matters, just peermax".
Plus almost everyone can get into a college, there is only really competition for a handful of elite schools. My college wanted SAT scores for admission, I did not take the SAT, they still admitted me without question. As long as you don't fail out your first two semesters in a row most colleges don't give two craps about your highschool performance.