Why would the electronic media need to be captioned if a captioner is already assigned to the class?
The same holds true for real-time captioners as for interpreters, it is very difficult for a student to watch the real-time screen and the electronic media at the same time. So the student misses a great deal of information by not being able to view the screen and the real-time text simultaneously as when it is captioned. Also, being that it is scripted it is presented at a much faster rate of speed than normal speech. This makes it close to impossible for the captioner to keep up with the scripted dialog and information is often dropped.
