Read Aadil Palkhivala's response:
The reason we face east is to receive the energy of the rising sun and the rotating earth. It is also perfectly acceptable to face north, since then we are aligning our bodies with the magnetic meridians of the earth. Thus, facing east aligns us with the energy of ascent, while facing north aligns us with the magnetic connection with the earth's core.
No matter which way you face, remember that alignment with your immediate environment comes first, then alignment with the external environment. Therefore, if you are in a square room with a corner that faces due east, align yourself with the room so as not to face the corner but to face as close to east as possible.
I recommend you go inside your heart and feel what is appropriate for your particular location. Whenever I enter a room, I turn on my "yoga sensors" to judge which side of the room I should teach from. After you develop your internal sensors, you will find they are more reliable than knowing where east and north are.
A different issue is the student-teacher relationship, and the respect a teacher must show for the student and the student for the teacher. I advise always giving students an unbiased ear, and then, taking their suggestions into consideration, following your heart.