Anything you can prep for - grades included - is going to trend towards being largely influenced by "who has the most time and money."
I don't have any good ideas to get away from that.
I don't have any good ideas to get away from that.
Or what matters most - who is willing to put in the effort.
You already have 6 hours a day in high school. Don't need more time than that. As for money, that's not needed either. Your high school math books will do. There's also the public library, the Kahn Academy, youtube, etc.
It's possible our declining academic performance is simply another artifact of rising inequality.