How do I decide what course level I should be in

The Practitioner program course levels are explained on the website.  Read carefully and reflect upon the descriptions given about each of the levels.  The recommended number of attendance terms at each level is an excellent guide for students.  Progress in Yoga is based on experience and therefore the number of hours we spend on our mats and in a classroom really matters.  It is easy under our western model of education to intellectualise about our progress and to interpret our development through the filter of our personality (our desires and fears).  The influence of the personality on interpretation of experience is exactly what Yoga advises us about: that mind is not able to observe the objects of life clearly.  Think carefully about the number of terms of practice experience that you have had and how much you practice at home.  Make a decision about what level to enrol into based on that information rather than where you think you should be or where you would like to be. If uncertain, consult your teacher.