To learn the physical movements of the form alone takes quite some time, depending on how often lessons are conducted and how regularly students practise. Remember not to teach too much too fast. Tai Chi is not about how much you know.
It is not practical to teach any of the six sets sequentially from beginning to end. It best to create little sections and circuits within each set that are performable and continuously repeatable in themselves yet still provide the benefits of deep breathing, exercising the body from the inside out and calming the mind. This benefits and encourages the student as they have something complete to practise and therefore can reap the rewards of a discipline, which trains the body, mind and spirit. It is also beneficial for the teacher in terms of being able to direct how other movements are joined in.