The settle command has a lot to do with synchronization, so it can be done successfully with a room full of untrained dogs. Of course if any of the dogs have had any kind of training it is that much easier...
Use a two sylabel word, and say the second part in a lower tone of voice. I like the word 'settle', but pronounce 'seddle' as that is softer. Use a calm voice and say it a little slower than normal. Relax your attitude/body as well, and ignore your dog... most will calm down within a minute or two, and if you are sitting they will lie down.
When I was in college, all 15 of us students had a service dog in-training with us all of the time, including through about 5 hours of lecture every day. We each had a few dogs at different ages around 5, 13, and 20 months, and we varied who we brought to class... sometimes every dog was between 2-6 months old, and no, we didn't run them around like crazy before class.
As soon as the humans were settled, the puppies would flop down under the tables at our feet until we woke them up when class was over. No command even needs to be used if you create the atmosphere.