eeeeh.

I'm not sure the structure is right....

Instructor stands alone... that's fine.
Courses are broad and general... like English. Or Programming 101. They should probably stand alone as well.
Classes are an instance of that course... Programming 101, MWF, 1:30pm
Classes are in a Location like PS203
Classes are taught by an instructor

I'd probably have an Instructor table, a Course table, a Location table, a Class table (with an FKey to Course table, an FKey to Location table, and an FKey to the Instructor table)
4 tables.

Instructor - Prof Smith
Course - Programming 101
Location - PS203
Class - Programming 101 on MWF @ 1:30pm in PS203 w/ Prof Smith

-tg

-tg