Mathematics was always my worst subject at school, right up until I went to college. I’ve heard a similar story from other physicists. I don’t know how useful my speculation about it will be to anybody else, but I think this is the reason why.
The kind of mistake I was prone to making, and the flaws in the way mathematics was taught, meshed perfectly. Carelessness cost more in math than in anything else, on the whole. If I was writing a history essay and I happened to swap Elba and St. Helena, I might only get docked a couple points out of a hundred, or perhaps none at all if the teacher had too many papers to grade. But if I wandered away from my pre-algebra homework, and upon my return my garishly awful handwriting had turned absolute-value bars into ordinary parentheses, my calculations would be completely off from that point onward. Nor did any of my teachers pick up on my problem — “Blake, you’ve got to be more careful!” — which makes me suspect that they weren’t much better at identifying what went wrong for other students, either.
In history and to a large extent in science, I was able to get by all through middle and high school with what I had learned out of books and documentaries on my own. (I was extraordinarily lucky to have a family that already had plenty of books around, and the means and the sense to provide me with more as I packed their contents into my brains.) I don’t think I had to learn anything in school that came across as wholly new. Everything was at most an elaboration of a topic I had already seen, something I’d grasped from a Larry Gonick cartoon guide, let’s say, done up with a few more details that might just have been included for the sake of having homework problems to assign. Algebra and geometry and trig and calculus, though, came closer to asking for a genuine production on my part.
Techniques of checking one’s work, which might have helped me to become a bit more generally competent, were either not taught or not motivated. “Plug your value of $x$ back in and check” might have been the last step of a few algebra exercises, but only because it was part of the rubric, devised to add another thing that could be graded.
The weird thing is that I had a sense of the importance of the mathematics, of the motivation for it. I knew why Kepler had cared about sines and cosines — to hear the music of the spheres, to turn comets from signs of dread into those of wonder. Exponentials tracked the explosion of populations and the decay of radioisotopes, each ominous in its own way. The subject offered wonders of pure thought and marvels of application. At the time, schoolwork merely seemed disconnected from those treasures which I saw in secondhand outline. Now, in retrospect, it appears almost a parody of them.