[jmkirby]

I'm old enough to have never been tested for dyslexia, because I scored high in average tests..

But come high school years, or in British sixth form studying for"A levels", I scored in the top decile for my class and for Applied Math, but the bottom dectile for Pure Math.

I think you can make a very good argument that math notation is not doing the potentially career changing job it could be doing, by not expanding the keys. Darn, even a key table index alongside would be night and day better. Edit - didn't remember the length of my comment after coming back to it after a break, so culled the excess. The punchline was that when we got a new young and enthusiastic Pure tutor, who was French, so he in true anger would explain to us in great eloquent depth, my marks equalized in two semesters.

There's surely something like a formal study of students to show if comprehension is the main reason math is hard?

[hyeonwho3]

At the level of arithmetic, there are studies of children performing math in the marketplace, but then being unable to do the same calculation on paper. So translation from notation to reality (and back) is probably a significant barrier to success in math.