Please take your high school courses seriously. Meet the HS diploma requirements for HS graduation.
Are you planning on applying to colleges, at some point? Colleges and universities aren’t going to consider your “hobby” of studying math. They’re going to look at your grades.
It’s all about grades in a classroom.
My husband loves math. He finds it “fun” to do proofs in his head. (His Caltech-father tutored him and his twin, in math, in Middle School).
While in high school, my husband took math courses at the local university (SDSU) and was required to take a math entrance exam.
(They ran out of courses, at his HS, at his level. He had already surpassed the community college level math courses.)
He did not struggle to learn the material and kept up with his AP courses and ECs. But because he had professors, he could gauge his progress and ability. Math has always been an “easy” skill for my husband. (Our kids are the same in their ability to calculate in their head. -Dad tutored them in math.)
If you’re at that level, then I say: “Yes, go ahead. Do it on your own and study”.
It’s not an EC, and it would only be for your benefit.
But if you’re struggling, that tells me that self studying is not beneficial for you or your time.