Review the item:
Jacques, a self-taught computer whiz, always hates going to his Introduction
to Microcomputers class the reason is that both his textbook and professor
are at least a year behind when they discuss
apps or artificial intelligence.
No punctuation of any kind is necessary between behind and when. That both his textbook and professor are at least a year behind is a subordinate clause. When they discuss apps or artificial intelligence is another subordinate clause.
When you attach one subordinate clause to the end of another, you seldom need punctuation.