Teacher’s Position in the classroom. Basic of basic = Actors don't look at the script on the stages.

acworksさんによるイラストACからのイラスト

Some teachers do their class lesson just standing specific narrow area in front of the class from the beginning to the end.
Why do they do so?
The most common reason is that

They can't run the class without looking at the "Instruction book" or "Teaching plan" on the teacher's desk.