-while that's certainly true, when people say they are "bad at maths" they usually mean exactly that they have to put in a lot more effort (=trying harder) to reach the same level of math skills as the "gifted" guys.
The ease of doing it in class or breezing through homework assignments was backed by hours a night of looking at high level concepts and talking about math with people more advanced than me, including teachers during lunch breaks and after school - a habit I'd had since late elementary school.
At the end of the day, they weren't "bad at math", I just put a lot more effort in to my practice - and it showed on game day, as it were.
Just like the guy in my school who was "gifted" at basketball spent hours a night practicing since early elementary school.
In college, I had to put in a lot more work, but the math still came somewhat naturally to me. I'm pretty sure I still had to put in less work than some of the other college students to reach the same level of understanding, though.
I neither put in as much work, nor reached the same level of understanding, as the 'gifted' college students, though.
edit: I just realized you said high school.
I picked high school though because most of the comparisons about being "bad at math" start around then. The reality is that I just put in more work than many people and was a class or two ahead of the average student up through the start of university, where I went on to study math (and was at a similar starting point with most other math majors at my particular school).
At the end of the day, I'm just an average fish in the math pond, but it's easy to think you're not as good if you don't see the work backing my talent in high school and base your comparisons for life on that (or even the first year of undergrad).