Electronic device in class

Why do some students have an accommodation to use an electronic device in class?

Some students have disability related barriers to taking notes and/or organizing information using a pen and paper. These students typically use an electronic device with a keyboard to take notes in class.

Some students also use assistive technology software on these devices which further reduces barriers to taking notes (i.e. screen enlargement software for a student with low vision).

I have a no devices policy in my course. Can I prevent a student with this accommodation from using their electronic device? 

No, as this method assists your student to obtain the same level of information as any other student in the class.