I hate to admit this as a teacher, but I didn't have a coworker to watch the class and had to leave them doing quiet work "alone" at their desks. I was in the next room with the door open so that I could hear everything going on. I hated leaving them - but also hated not having prep time to pump.
Thanks for the good advice everyone! Hopefully, I can work together with my administration to find a better solution for the next time around