that’s literally what I did too and (not to brag but) I got on my country’s international math team and got free admission to university because of that. But how many were there? 10 at most.
Edit: my point is that finding the right math club at the right time is even more luck and effort than getting good on standard tests.
Oh sorry, to be clear "math club" here was supposed to mean like, local math club, not successful competitive math club.
I mostly convinced classmates to go to local competitions because it was a day out of class and we could stop by the mall afterwards. We didn't win jack shit, my crowning "achievement" was beating half the schools at a regional competition, which is typically teams of 4, but as a team of 1 (and there's no award for 50th percentile).
Nonetheless, I had "President - Mu Alpha Theta" on my college application and I did end up making it to an elite university.
Edit: my point is that finding the right math club at the right time is even more luck and effort than getting good on standard tests.