Voice classes run a little differently than piano and the other instruments.
We start with vocal exercises from the Blaylock Vocal Method and we sing them together.
Then for junior students they work at their own station on their own learning journey (song work, ear training, theory, etc.) And yes they all sing at the same time on different things. It builds focus and the ability to stay on your part with other distractions. Classes include exercises, individual work on theory, ear training, whatever song they are working on, and then we play a game together.
With teens and adults, we do the individual work after exercises and then either continue with individual singing with the teacher floating around giving coaching, or we have a masterclass style format where one singer gets coached by the teacher, while the others observe and everyone gets some time being coached. The second is what we do the most as we find it works the best.
If you're hired and going to teach voice, you'll get training and support on how the model is different for voice and in the Blaylock Vocal Method. :-)