The student should ideally be present for all 180 contact hours. Usually a trainer would include in their T&Cs, the minimum attendance to graduate (usually around 90%).
If a student falls below this, then it is recommended that the student can either be deferred to the next cohort, or they can pay an additional fee to do one-to-one catch ups with the lead teacher, to go over what they have missed.
Ultimately it is up to the Senior Yoga Teacher to decide your criteria for passing the course, so they can create whatever structure and boundaries as they wish. We recommend that this is added into the T&Cs of the course.