There are very few Yoga systems, which concentrate on and assess their yoga teachers on the ability to understand and teach correct body mind breath relationships in appropriate posture work. The Iyengar System of Yoga is the only system with a detailed and arduous training and certification process in posture work for yoga teachers.

A minimum of 6 years of structured practice and training are required before you can be assessed for teaching ability. You must pass a practical exam from an internationally affiliated body before you can assert to the public that you teach Iyengar yoga.

New students to yoga are generally not aware of what exactly yoga is and how to best assess a teacher. So usually teachers are assessed by the students personality preferences and avoidances. This may lead to finding an agreeable experience in a "yoga" class but it may not relate to the actual practice of yoga. Yoga does not have to be unpleasant but it does have to create the correct changes in the body, awareness, health and heart of the student to be a yoga practice.