As a student I definitley notice when a teacher has pre planned his/her class. It is not hard to tell when there is an emphasis either on a particular area of the body or group of like poses. I would also like to say that this works for a good many students however the teacher needs to be sensitive to when their class plan is not working well for the students. I have seen times when a teacher will come to class wanting to work on poses that require a good deal of strength at 7:00pm on a weekday when most of her students are tired from work, school, etc. I have also seen teachers who come to class with a plan to work on more advanced poses only to find out that the majority of the pupils in the class physically cannot do what is being demonstrated. Now of course most teachers will see these issues and adjust the class accordingly however threre are some out there who don't and from my experience, these are usually the scenarios where one would see a few students who have no problem rolling up their mat and leaving the class.