I did have a student in my last class who said she was "dyslexic"...but at the end of the class. I often wondered how she could be so attentive in class & do so poorly on the exams & quizzes.
I now know if I see this behavior again I will ask about disabilities. I think a student should notify the instructor that there is a learning ability at the beginning of the new term. This way accomodations can be made at the start of the term, not the end.