None of these grades necessarily correlate to skill/mastery in those subjects when schools are given liberty to inflate grades as much as they please. That's the entire reason why GPA is less important in the college applications process than admissions exams like the SAT & ACT.
That's not to say that it's a good idea to have a thread where people post those scores. All that serves to do is abate people's confidence using something that doesn't show how good of a person you are or even necessarily how smart you are. Many people with very high scores on tests like the SAT are able to get them because their brains function in a way that is conducive to performing well under pressure and working quickly, not necessarily because they've worked the hardest in school.
So yeah, if you have good grades, congrats, keep it up. If you have lower grades because you go to a school with tougher curriculum and harder classes, don't feel like other people with higher marks are better students than you just because their percentage is higher.