Unfortunately you couldn't start "computing the impulse response of a filter" when you were 12 but if you could, and you continued to practice it daily, you would be very capable compared to people who just started in university.
Going further, I would argue that most people I know who've been programming since they were 12 weren't even writing very good code at 22 (or whenever they left college and entered the working world). It's vanishingly rare that people were writing flexible, maintainable code in their teens. It's much more common that they were coding to scratch an itch, and that their code only solves the pieces of the problem they cared about, and probably not very well.
Note: I've been programming since I was 12.
At that age, your code is going to be a mess no matter what tools you use, so you might as well have an excuse.
(Seriously: there's some brain development that doesn't happen until the close of puberty, and I believe that some of that is necessary for most people to plan and write maintainable code)