My dad sold the IVR to the School back in the late 80's early 90's that eliminated the Drum registration.
I had a special TEX number that I used to call into, thanks dad!!!! I don't ever recall having much trouble in getting the classes that I wanted.
For those that are interested in the technology, it was run off of a Nortel DMS-100, or what would be known as a Private Switch the size of a Central Office. Centrex was big back in the day.