When a student comes to the mat, there’s an implied contract they make with you as teacher. Staying safe, honoring one’s self, and practicing ahimsa (non-harming) is of primary importance.
As teachers, however, we cannot be wholly responsible for our students’ safety. We need to teach them to take responsibility for themselves and to build self-awareness. This may mean learning and respecting their limitations, learning to self-adjust, and practicing with less ego and more love for their wellbeing.