I can’t think of a reason why not knowing computer science already should stop you, especially in high school. That’s especially true for the more theoretical portions. I would claim that the only people with a significant head start over you are the very top students in international mathematics competition or children of CS and math professors.
First, theoretical computer science is about theory. Coding is about practice. Their foci are disjoint.
Second, while much is made of people who start coding in their teens, quality undergraduate can be a great equalizer, and many of the people I’ve worked with didn’t learn until then. In contrast, a few people I’ve known (but not all) who started coding in their teens built up awful habits and couldn’t shake them when put in a professional environment. The same goes for mathematics knowledge.
There might be other reasons to not study computer science, but not having learned it by high school isn’t one.