As a dyslexia tutor, I have often witnessed the difficulties that my dyslexic students have with math. My fellow dyslexia tutors see this issue on a regular basis as well. The reason for these difficulties is the fact that the same challenges faced by a dyslexic with written language apply to mathematics as well. Students with dyslexia often have difficulty with numbers in the same way that they have difficulty with letters.
Additionally, a dyslexic may have a very difficult time with a word problem based math cirriculum, simply because they are unable to read and clearly understand the questions. In a normal reading setting, this lack of understanding makes it difficult for the student to understand what is being said; in a math setting, it makes it almost impossible for the dyslexic student to do the problem correctly. In a word problem, where every little word can have a mathematical process associated with it, there is that much room for error if a dyslexic doesn’t understand everything perfectly.
When helping a dyslexic student with math, it is important to keep in mind that the challenges they face with language also apply to math. With practice and repetition, a dyslexic student can definitely succeed in math, but they may acquire material at a different rate and with different methods than other students.