Hello Julie.
Several points.
First I am always concerned when a yoga teacher considers teaching something they are not fully comfortable, trained, and prepared to teach. I see a myriad of posts (elsewhere) asking "how do I teach the elderly, how do I teach people with hip replacements. or “I just accepted a class teaching porcupines and have no idea how to adjust them”. I am not referring to being nervous about teaching. I am referring to being qualified to take an offered position. So please consider whether this pertains to you or not and go yogically from there.
My second point is an energetic one. I personally find that teaching back-to-back classes does not give ME the needed time to refresh my cup, get grounded, clean myself, and have as much to offer group two as I did group one. Therefore I rarely accept opportunities that involve back-to-backs unless there is 30 minutes between and I can shower, eat, and hydrate between sessions.
Third is the definition of beginner and intermediate relative to yoga or asana, I’m not sure which you are teaching. Beginning students have very little sense of their own bodies, very little sense of them spatially, no alignment or foundation, and lack the ability to focus and breathe. As such they are taught based on these things - so class is about feeling (not perfecting), breath, focus, and learning about their body in space.
The next level of student is level one, then intermediate so the intermediate is two levels up from beginner. For these students they should not need reminders of breath. They should be able to remain still in tadasana without being furtive in body or mind. They should have fundamental actions and alignments in standing poses without being cued, and they should have the appropriate actions to protect the knee, hip, low back, shoulder, and neck. These students should have learned the basics of pranayama in level one and are ready for intermediate asana - Vira III, Parivrrta Ardha Chandrasana, Pincha Mayurasana, Janu Sirsasana, Ustrasana, et al.
This having been said, most fitness centers are not at all discriminating and do not care what you teach. It is only our deeper sense of ethics, respect, and integrity that matter - and the safety of the student of course.
gordon